The process of methanol synthesis carried out by chemical reactors consists of an exothermic catalytic reaction able to release great heat amounts; in order that the working temperatures inside the reactor can be maintained in a range useful to the synthesis, it is needed that said heat is removed outside the same reactor.

In order to remove the heat emitted during the synthesis process, the reactor is made up of an outer shell and an inner wall, such that both the flow of the synthesis fluid and of a cooling fluid (for example water) is allowed.

Said inner portions can be made up of exchanging pipes, which constitute a tube bundle, in turn made up of manifolds, supports and other components aiming at the thermal exchange and the mechanical seal. In such a configuration, the process fluid flows on the shell side while the exchange one inside, or vice-versa according to the first hypothesis, the process fluid is introduced by a suitable connection and distributed in the reactor volume on the shell side by a central pipe having many holes, and then flows radially towards a second order of connections, encountering in the meanwhile the catalyst (which is not dragged towards the second order of connections thanks to a suitable peripheral screen) , which is charged on the shell side as well and surrounds the exchanging pipes; so the exothermic synthesis occurs in the path area starting from the distributor central pipe towards the second order connections, and the heat produced is removed by means of the exchanging pipes, inside which the cooling fluid flows.

The tube bundles are supported by suitable diaphragms and supports, which discharge the transmitted mechanical forces as well, first to the jacket and then to the shell.

Each bundle is made up of independent groups of exchanging pipes which have an equilateral triangle pitch arrangement in their central section; for this reason it is needed that the exchanging pipes are arranged according to concentric crowns at the tube plate and that they have a double bend at their respective ends. A similar configuration usually leads to great problems connected to proved assembly and construction difficulties: it is in fact needed to bend the pipes first from both the sides, than they are introduced in the shell starting from the bottom of the reactor; subsequently after the introduction of each row is ended, the diaphragms are assembled in the shell. Exactly in this last passage the main critical problems occur, since the last diaphragm intended to be assembled in the shell, resulting from the composition of all the single pieces row by row, needs to be very rigid in order to resist suitably to the pipes, both in the transporting step and the functioning step of the reactor: in addition, the described features of the last diaphragm make it necessary to work in usually very small spaces during the introduction steps of the last row of exchanging pipes.

The object of the present invention is to provide an easier solution from a practical and working point of view.

The innovation of the present invention will be highlighted in the following detailed description which refers to the drawings 1/3 to 3/3, and in particular :

- figure 1 represents the vertical section of a preferred embodiment of the invention;

- figure 2 represents a detail of the bend of the pipes introduced in the tube plate;

- figure 3 represents the horizontal section of a preferred embodiment of the invention, at the level of one of the diaphragms; - figure 4 represents the horizontal section of a preferred embo ^' diment of the invention, at the level of the tube plate;

- figs. 5/a, 5/b, 5/c represent the bend sequence of the pipes, as proposed by the invention.

As previously stated, the solutions known at the state of the art impose that the bending of the two ends of the exchanging pipes 2 occurs on the ground and only after these ones are introduced in the shell 1, with all the practical consequences yet described.

The solution of the present invention provides the bending on the ground of the pipes 2 from only one side, before being assembled in the shell 1, by means of a suitable pipe-bending machine; according to this configuration, the diaphragms 5 are introduced in the shell 1 in their final configuration; in the following, as it is well shown in the sequence provided in figs. 5/a, 5/b and 5/c the exchanging pipes 2 are introduced in the shell 1 from the straight side, passing through all the diaphragms 5, previously positioned, and finally the bending is carried out from the outlet side by the diaphragms 5.

More specifically, the proposed mounting sequence provides firstly the definition of the length of the jacketed shell 1 in a suitable manner to provide the full cover of the whole area where the diaphragms 5 are installed; subsequently the exchanging pipes 2, which are part of the first tube plate 3, are introduced, starting from the inner crowns.

For clear dimensional reason, the pipe-bending machine needs to work in outer position with respect to the bundle 4.

Each pipe 2 is introduced until reaching the final position of the bends, subsequently it is pushed until it comes out from the shell 1 of a length equal to the bending one plus a minimum over-length (figure 5/a) , than it is bent by a suitable machine (figure 5/b) which is positioned such that the pipe is blocked and which is able to carry out contemporarily the two bends, than it is introduced again inside the shell 1, also applying a light rotations if needed, until reaching its definitive position (figure 5/c) .

Eventually, once the described operations are ended, the tube plates 3 fixed to the two ends of the pipes 2 are positioned and anchored to suitable semispherical manifolds 6.

The preferred embodiment here described proposes a solution implemented by using four tube bundles 4, but it is also possible to apply the described method in other configurations, constituted by a different number of bundles 4.

The final result deriving from the application of the mounting sequence object of the present invention leads undoubtedly to more rigidity of the diaphragms 5 with respect to the traditional configurations, provided that these latter are made up of only one piece. It is also clear a simplification of the mounting operations such that it is possible a result with the same functional characteristics as those already possible using methods known at the state of the art, but able to function in more contained spaces and strongly reducing the time needed for the mounting operations .