FI86916B - Arrangement for carrying out physical and/or chemical processes, in particular continuously-operating heat exchangers - Google Patents

Description

8691 6

Apparatus used to carry out physical and / or chemical processes, in particular a continuous heat exchanger

The invention relates to an apparatus for carrying out physical and / or chemical processes, in particular to a continuous heat exchanger comprising a bundle of parallel, vertical risers, an upper chamber, a lower chamber, upper and lower tube plates for open contact of the tube bundle with the upper and lower chambers, respectively. keep in a fluid state at least in the risers by means of a fluid flowing upwards during use through the lower chamber, risers and the upper chamber for the granular mass of the distribution plate in the lower chamber and at least one return pipe opening below the distribution plate to return the Equipped with an inflow section extending into the lower chamber from the lower tube plate to a plane above the distribution plate through which the return pipe or pipes protrude, and wherein the lower chamber is provided with a device which prevents the granules from entering the fluid inlet of the lower chamber during stopping.

This type of device is known from D.G. From an article by Klaren in "Fouling Prevention Research Digest",

Butter. 5, no 1, pp. III-XVII (March 1983). A known heat exchanger which has a high efficiency due to rupture of the rivet membrane along the inner surface of the risers due to the fluidized bed is of primary interest if a layer of material can precipitate from the fluid on the inner surface of the risers, preventing heat transfer through the riser walls. Such a barrier layer does not precipitate in the known device due to the abrasive effect of the granules. This device is therefore ideal for use in the food industry, for example.

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Granular mass, on the other hand, causes its own disadvantages. A drawback of the known device is described below.

The granular mass circulates upwards through the risers and downwards through the return pipe. During this cycle, and in particular during use, the granules are also in a vortex motion in the lower chamber, which apparently causes very high wear of the material at the junction of the heat exchanger jacket, in particular the cylindrical wall forming part of the jacket.

According to the invention, this drawback is eliminated by means of a second distribution plate arranged in the lower chamber, at a level below the outlet opening leading to the lower chamber of the return pipe.

In this proposed construction, in contrast to the known device, the device which prevents the granules from entering the fluid inlet in the lower chamber during stopping cannot act as a shut-off valve against the lower edge of the return pipe. Under all conditions, therefore, a downward flow of fluid flowing inside the return pipe, which can be n.

25 * from the mass flow of the fluid fed to the inlet of the heat exchanger. For this reason, the average logarithmic temperature difference inside the risers is less advantageous, which requires the installation of a larger heated surface in order to achieve the desired efficiency.

The latter requirement can be eliminated to some extent according to the invention by placing a plurality of distribution plates at a level above the outlet opening leading to the lower chamber of the return pipe, preferably so that the different distribution plates are not vertically aligned.

3 8691 6 It appears that the downward flow of fluid through the return pipe or pipes can thus be limited by n.

15 3 i i n n mass flow through the inlet of the heat exchanger.

Absence of moving parts in the lower chamber, te. the fact that the device which prevents the granules from entering the inlet leading to the lower chamber of the fluid during stopping is not implemented as a valve, and the lower wear of the parts of the lower chamber compensates for the disadvantage caused by the circulation of fluid through the return pipe.

It has been proposed to provide the inflow pipe section with side drilling at a level in which there are no granules in the lower chamber during use in the fluidized bed. with only a fluid medium present. If heavily fouling fluids are used, e.g. solids containing solids, the side drilling may become clogged, causing the layer in the riser to sink down and the riser to eventually begin to act as a return pipe, which must be considered harmful.

In the method of operating a device of the type described at the outset, this last drawback has been avoided by temporarily reducing the pressure of the fluid at the top of the lower chamber.

The invention will now be described with reference to the drawing, in which Figure 1 shows a first embodiment of the invention, and Figure 2 shows a second embodiment of the invention.

Figure 1 shows a first embodiment of a device according to the invention. The heat exchanger 10 has an inlet 11 and an outlet 12 for the first fluid and an inlet 13 and an outlet 14 for the second fluid. Inside the jacket 15, the lower chamber 17 is connected to the inlet 11 and from above the chamber 16 communicates with the outlet 12. The upper 4 196916 pipe. a riser bundle 18 comprising a return pipe 21 is arranged between the lower pipe plate 20. The risers are provided with a weather pipe opening 11a 22 extending downwards from the lower pipe plate 20 into the lower chamber 17. The inlet pipe sections have side bores 23 below and above the return pipe outlet. The lower chamber 17 is further provided with a device 41 which prevents the granules in the lower chamber, the riser, the upper chamber chamber and the return pipe from entering the inlet 11. The granules can in any case be brought into the fluidized bed space 18. The lower end of the return pipe 21 must contain immobile granular mass 27.

In order to prevent excessive wear of the jacket material, in particular at the joint between the bottom cover 43 and the cylindrical wall 44 due to the vortex movement of the fluidized bed granules in the risers, a second distribution plate 42 is arranged in the lower chamber 17. , consists of a simple hood 41 which is fixedly mounted and which divides the fluid medium from the inlet 11 laterally through the lower chamber 17.

During the stop of the heat exchanger, the main part of the granular mass is located in the lower chamber below the first distribution plate 24. At start-up, the fluid flow from inlet 11 tends to follow the least obstructed route. Initially, the fluid flows mainly through the return pipe 21, but as the fluid flow converts the granular mass to fluid, the fluid passing through the return pipe gradually encounters increasing resistance, causing the fluid to rise in the risers 18 as the granular mass rises within the flow. As the mass flow of the flowing medium 5 8691 6 increases, the fluidized layers in the risers 1Θ rise faster than the fluidized bed inside the return pipe 21. This is due to the non-bores 23 of the inflow pipes 22, which make the fluidized bed inside the risers more porous than the layer inside the return pipe. The fluid granular mass in the risers first enters the upper chamber 16 and flows over the return pipe 21, through which the granular mass and the fluid begin to flow downwards. In the lower chamber 17, the downward flow between the distribution plates 24 and 42 through the return pipe 21 and the upward flow of fluid from the inlet 11 are mixed, and finally a balanced state is reached in which the volume of fluid leaving the heat exchanger through the outlet 12 is equal to the volume through the inlet 11. , and the granular mass circulates through the risers 1Θ and the return pipe 21. During the cycle, the risers 1Θ contain less granular mass than the return pipe 21. In order to reduce the adverse effect of the fluid flow through the return pipe on the average logarithmic temperature difference, the circulation of this medium through the return pipe should be as small as possible. The increase in the pressure difference between the upper and lower chambers contributes to the reduction of the fluid flow through the return pipe. The pressure difference is increased by fitting a plurality of distribution plates to a level above the outlet leading to the lower chamber of the return pipe, preferably so that the openings of the plurality of different distribution plates are not vertically aligned.

Fig. 2 shows a structure 45, 46, 47 comprising several distribution plates in the lower chamber 17 above the outlet of the return pipe 21.

Claims (3)

8691 6 6 Apparatus for carrying out physical and / or chemical processes, in particular a continuous heat exchanger comprising a bundle of parallel, vertical risers (18), an upper chamber (16), a lower chamber (17), an upper tube plate (19) and a lower tube plate (20) for open connection of the tube bundle (18) to the upper and lower chambers, respectively, a granular mass (27) which can be kept in a fluid state at least in the risers by a fluid flowing upwards through the lower chamber, the risers and the upper chamber; ) for the granular mass and at least one return pipe (21) with an outlet below the distribution plate for returning the overflow of granules above the plate from the upper chamber to the lower chamber, each riser being provided with a 3 inlet to the level through the distribution plate of the return pipe protruding or return pipes. protruding, and the lower chamber is provided with a device (41) which prevents the granules from entering the inlet opening (11) for the fluid of the lower chamber during stopping, characterized in that a second distribution plate (42) is arranged in the lower chamber (17). to a level below the outlet leading to the chamber. Device according to Claim 1, characterized in that the distribution plate (45, 46, 47) in the plane below the outlet of the return pipe (21) in the lower chamber (17) is arranged in multiples and preferably in such a way that a different division of the multi-plate structure. The openings (45, 46, 47) are not vertically aligned. A method for operating an apparatus for carrying out physical and / or chemical processes, in particular a continuous heat exchanger, comprising a bundle of parallel, vertical risers (18), an upper chamber (16), a lower chamber (17), an upper tube plate (19) and a lower tube. 6 a tube for open connection of the bundle of tubes (20) to the upper and lower chambers, respectively, a granular mass (27) which can be kept in a fluid state at least in the risers by a fluid flowing upwards through the lower chamber, the risers and the upper chamber. (24) for the granular mass, and at least one return pipe (21) having an outlet located below the distribution plate to return the overflow of granules above the upper tube plate y.1 from the chamber to the lower chamber, each riser being provided with an inlet pipe section 11a (22) extending from the lower chamber the top of the distribution plate to the side plane through which the return pipe or return pipes protrude. protruding, and the lower chamber is provided with a device (41) which prevents the granules from entering the inlet of the lower chamber for fluid during stopping, characterized in that the pressure of the fluid in the upper part of the lower chamber (17) is temporarily reduced.