Method for emptying fixed-bed reactors

BENEFIT OF EARLIER FILING DATE UNDER 37 CFR 1 78(A)(4)

This application is a continuation of Ser. No. 09/566,613, filed May 9, 2000, now abandoned, which is a continuation of Ser. No. 09/054,359, filed Apr. 2, 1998, now abandoned, which is a continuation of Ser. No. 08/670,917, filed Jun. 26, 1996, now abandoned, which claims the benefit of Ser. No. 60/000,620, filed Jun. 30, 1995.

1. Field of the Invention

This invention relates to a method for removing a spent catalyst from a fixed-bed reactor, more particularly from a tube-bundle reactor.

2. Description of the Related Art

Deactivated catalysts in fixed-bed reactors have to be removed from the reactor at predetermined time intervals. The catalysts may be present in the reactor both in powder form and in the form of hard lumps through disintegration, sintering or caking. The fixed-bed reactors are normally emptied by opening of the reactor base and destroying the caked catalyst with water under high pressure introduced from below. Cleaning is carried out in an open system. Catalyst sludge and rinsing water leave the reactor without any control. Even if the reactor is emptied with care, contamination of the area around the reactor with catalyst sludge cannot be avoided. The catalyst collected in open containers has to be transferred to suitable drums for disposal as waste.

Accordingly, the problem addressed by the present invention is to provide an improved process of the type mentioned at the beginning which would not have any of these disadvantages.

According to the invention, the solution to this problem is characterized in that a suction hose, in which a high pressure hose comprising a high-pressure nozzle is integrated, is introduced into the reactor, the catalyst is then size-reduced by water under high pressure passed through the nozzle, the catalyst/water mixture is removed under suction and is optionally collected in a separator.

3. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a tube-bundle reactor having an apparatus for removing the catalyst/water mixture.

FIG. 2 is an enlargement of the catalyst/water removal apparatus.

FIGS. 3-5 depict various arrangements of the filters in the separating unit.

One example of embodiment of the invention is described in detail in the following with reference to FIGS. 1 to 5 of the accompanying drawings.

According to the invention, a fixed-bed reactor, for example a tube reactor ( 1 ), is emptied with water ( 2 ) under pressure to break up caked catalyst ( 3 ). At the same time, the catalyst/water mixture is removed under suction into a suitable separator ( 4 ) in a closed system (FIG. 1 ). The arrangement for emptying fixed-bed reactors 1 consists of a suction hose ( 5 ) with an integrated high-pressure water nozzle ( 6 ), a solid/liquid separator ( 4 ), optionally with an integrated filter for separating the rinsing water ( 2 ), a vacuum generator ( 7 ) (water ring pump, Roots fan or the like) and a high-pressure pump ( 8 ) for producing water under high pressure (FIGS. 1 and 2 ). To empty the reactor (fixed-bed reactors of the shaft or tube-bundle reactor type), only the upper reactor flange or a manhole is opened and the suction hose with the integrated high-pressure nozzle is introduced. The configuration of the high-pressure nozzle is such that the water under high pressure destroys caked catalyst, in addition to which a drawing-in effect of particular advantage in the case of tube reactors is also obtained through rebounding of the water jet. When the suction hose is withdrawn, the supply of water under pressure is interrupted. The catalyst/water mixture is separated from the air stream in a vacuum-tight separator ( 4 ). Vacuum-tight containers, authorized road transport containers (capacity 4-16 m 3 ) or even silos with and without discharge systems may be used as separators. The separators may also be provided with a filter ( 9 ) for separating the rinsing water (FIGS. 3 to 5 ). The filter may even consist, for example, of a metal cloth ( 10 ) and/or perforated metal plate ( 11 ). In this way, water can easily be removed from the catalyst sludge before transport.

The following operating data is proposed for the safe operation of the suction system:

In a test arrangement for the suction emptying of a pilot tube reactor for the hydrogenation of methyl esters, the best results were obtained with the following operating data:

A reaction tube with a catalyst volume of 20 liters could be emptied and cleaned in about two minutes.