CS205060B2 - Method of and apparatus for cooling splitting gases - Google Patents

Description

The invention relates to a method of heat exchange, in particular for the cooling of fission gases, wherein the flowing heat exchange medium transfers its heat to another flowing heat exchange medium by means of an auxiliary medium.

Such a heat exchange process takes place. has long been used in nuclear heat exchangers. power plants (see Liquid-Metals Handbook, Sodium Na-K Supplement, Atomic Energy Commission, Department of the Navy, Washington, D. C. of July 1, 1955). The heat exchange takes place here between liquid Na and NaK or between NaK and water by means of a liquid metal auxiliary medium, mercury being used as the auxiliary medium. In addition to its function as a heat transfer medium, mercury has the task of protecting the operator from the dangers that may arise from the passage of the medium in the heat exchanger tubes if both heat exchange media arrive in the heat exchanger. direct. contact. In order to accomplish this task, in known heat exchangers, it is necessary to maintain the working medium of the auxiliary medium constantly at the maximum filling level, so that there can never be direct contact between the heat exchange media.

However, this process known from nuclear technology does not provide the ability to regulate the heat exchange capacity of the apparatus. It is therefore unsuitable for other thermal exchange processes, especially for the cooling of hot fission gases.

The fission gases are produced in a known thermal manner. cleavage. hydrocarbons in the presence of an inert gas (water vapor, carbon dioxide, etc.), by hydropyrolysis of preferably heavier hydrocarbons in the presence of hydrogen which is involved in the reaction or also by catalytic cleavage and is required after the reaction. cool the reaction. This results in more or less intense formation of petroleum coke on the hot surfaces of the heat exchanger, which makes it necessary to decarbonise the apparatus from time to time.

The tendency of the fission gases to form petroleum coke and hence the interval of the decarburization process necessary depends on the starting product used (diesel, gas oil). Since the known heat exchange processes do not allow the control of the heat exchange power, it was not possible to optimize the 'operation time' of the apparatus between the required decarbonisation processes depending on the product to be processed using these 'processes' to cool the fission gases.

It follows that, in this case of use, it is not possible to decarbonise the heat exchangers by the on-line decoking process without first discharging the cooling water. The on-if-dec50ing decarbonisation process is carried out in a known manner by incineration or gasification of coke with an air-water vapor mixture or also by steam only at high temperature, whereby gasification or combustion of petroleum coke deposited on the heated surfaces occurs. The “on-line-decoking” process avoids the otherwise very time-consuming mechanical cleaning of the heat exchangers, which in principle requires the opening of the heat exchangers by dismantling the gas closures. In one heat exchanger operating in a known manner, the high-pressure parts of the apparatus and the parts which are in contact with water using the on-line decoking method due to the good thermal conductivity of the auxiliary medium have been exposed to very high temperatures, resulting in damage to the apparatus as a result protective layer of magnetite (FesOi) on the water side of the apparatus.

SUMMARY OF THE INVENTION The object of the present invention is to provide a method and apparatus of the aforementioned type which allow the regulation of heat exchange power and, moreover, it is suitable for performing on-line decoking of heat exchange surfaces using an apparatus for cooling hot fission gases. previously drained the cooling water.

This object is achieved by the heat exchange method according to the invention, the principle being that the working charge of the heat exchange auxiliary medium is changed by admitting or withdrawing the medium.

Any suitable heat transfer medium, especially liquid metals, may be used as an auxiliary medium. Low melting metals, especially heavy metal alloys, are preferred.

If the auxiliary medium is drained, the effective heating or cooling surface, the size of which determines the heat exchange capacity of the apparatus, is reduced. On the other hand, when the auxiliary medium is admitted to the apparatus, the effective heating or cooling surface is increased, which causes an increase in the heat exchange capacity. In this way, it is possible to control the heat exchange capacity depending on the nature of the products being processed. Thus, when the process is used to cool fission gases, the temperature at the gas outlet side can be adjusted according to the tendency of the fission gases to carbonize in order to achieve a permanently long operating time between decarbonization processes се. In this case, the decarbonisation of the apparatus is completely drained off, so that there is practically no heat transfer to the pipes flowing through the cooling water. Thereafter, the heat transfer surfaces are heated by means of steam or water-air mixtures, resulting in gasification or combustion of the deposited petroleum coke. The parts of the apparatus flowing through the water are not exposed to high temperatures, so that the possibility of damage to the apparatus by destroying the protective layer on the water side is eliminated. In this way, it is possible to carry out the decarbonization without first draining the cooling water, so that it is possible to size. ...........

I can quickly change the process from cooling to decarbonisation.

The working medium of the auxiliary medium can be changed according to the invention in a quick and simple manner. The auxiliary medium is pumped out under the effect of pressure and allowed by a natural gradient. This ensures a quick regulation of the heat exchange capacity.

In order to carry out the proposed method, the invention further encompasses a heat exchanger device consisting of heat exchange tubes which are flowing through or bypass the heat exchange medium and which are surrounded or externally by auxiliary heat transfer elements which are flowed or bypassed by another heat transfer medium. The heat transfer means are provided with a heat transfer cartridge according to the invention, the principle being that the auxiliary elements can be connected to the auxiliary medium reservoir by means of an inlet or a discharge valve so that their working load can be changed.

According to another design of the invention, the heat transfer auxiliary elements can be connected to a pressure source. The auxiliary medium reservoir is located higher than the heat transfer auxiliary elements. The heat transfer auxiliary medium can be extruded from the auxiliary elements by a pressure source, such as a nitrogen battery. The inflow of the auxiliary medium takes place on the basis of a natural gradient which is formed between the container vessel and between the auxiliary elements.

The proposed design allows various designs of auxiliary elements, which can surround individual heat exchanger tubes or even multiple tubes as required. In an expedient embodiment, it is provided that the heat exchanger tubes are arranged in rows surrounded by plate-shaped auxiliary heat transfer elements. In another embodiment of the process according to the invention, each heat exchanger tube is surrounded by a coaxial, heat transfer tube auxiliary element. It is also possible within the scope of the invention to use so-called fixed tubes as heat transfer tubes.

Hereinafter, the invention will be explained in more detail by means of several exemplary embodiments. In the drawings:

FIG. 1 is a schematic illustration of a fission gas tube heat exchanger with an auxiliary medium reservoir located above and a nitrogen battery for admitting and evacuating the auxiliary medium.

FIG. 2 is a longitudinal section through the heat exchanger along line II-II in FIG. 1;

FIG. 3 is a cross-sectional view of the heat exchanger along line III-III in FIG. 2;

FIG. 4 is a longitudinal sectional view of the heat transfer auxiliary element of the heat exchanger of FIGS. 1 to 3;

FIG. 5 is a cross-sectional view of the heat transfer auxiliary element along line V-V in FIG. 4, FIG. 6 of another embodiment of the heat transfer auxiliary element of the tube-in-pipe structure shown in longitudinal section;

FIG. 7 is a cross-sectional view of the auxiliary element taken along line VII-VII in FIG.

FIG. 8 is a longitudinal sectional view of a further embodiment of an auxiliary element for a heat exchanger of a fixed tube structure;

FIG. 9 is a cross-sectional view of the heat transfer auxiliary element along line IX-IX in FIG. 8;

FIG. 10 is a longitudinal sectional view of an auxiliary heat transfer element, an incandescent boiler.

The device according to FIG. 1 consists of a fission gas cooler 1 which is connected via lines 2 and 3 to a steam drum 4 and via lines 5 and 6 to a liquid metal container 7. This container 7 is provided with a heating device 8, heated by steam or electrically, which keeps the metal in the container in a liquid state.

There are inlet valves 9 and a discharge valve 10 in the lines 5 and 6. Between the fission gas cooler 1 and the inlet valve 9 there is a pipe branch 11 in which a shut-off valve 12 is installed. The pipe branch 11 leads to a nitrogen battery 13 pressure and is filled with compressed gas. nitrogen.

The fission gas cooler 1 consists of a housing 14, an inlet gas chamber 15 and an outlet gas chamber 16 (see FIGS. 2 and 3). Several rows of heat exchange tubes are arranged in the interior of the housing 14 and each row of tubes is surrounded by a plate-shaped heat transfer aid 18.

As can be seen from FIGS. 4 and 5, the heat exchange tubes 17 are welded at their ends into the distributor 20a and 20b. The header and the distributor are laterally led out of the auxiliary elements 18 and have flanges 21 connected thereto via a compensator 22 'to the panel of the auxiliary elements 18. These are further provided with an inlet orifice 23 and a discharge orifice 24, 25 connected to line 5 and the discharge ports 24 are connected to line 6 via a header 26 '.

The collectors 19a and 19b and the distributors 20a and 20b are in communication with the pipes 2 and 3, respectively, via the main collector 27a and 27b or the main distributor 28a and 28b.

The fission gas to be cooled enters the interior of the heat exchanger through the gas inlet throat 15, bypasses - the plate-shaped heat transfer auxiliary elements 18 here and again exits the gas outlet throat 16. At the same time, the cooling water from the steam drum 4 flows through line 2, main distributor 28a and 28b and distributor 20a and 20b to cooling tubes 17, then flows in the form of a mixture of water and steam and continues to collectors 19a and 19b through main collector 27a and 27b. and via line 3 again to the steam drum

4.

The heat transfer auxiliary elements 18 have a liquid metal charge which fills the space between the auxiliary elements 18 and the water cooling tubes 17 and represent a very good thermal conductivity connection between the cooling tubes 17 and the plate bodies of the auxiliary elements 18 around which gas flows.

The heat exchange between the hot fission gases and the cooling water is thus effected by means of a liquid metal charge. As the liquid metal, low melting metal, preferably heavy metal alloys, is used herein.

The heat transfer capacity of the device can be controlled by changing the working load of the heat transfer auxiliary elements 18. For example, if the heat transfer power is to be reduced, a portion of the charge is drained through the discharge port 24, when the discharge valve 10 is closed when the inlet valve 9 is closed and the charge is pushed out of the nitrogen battery 13 by switching the shut-off valve 12. the heated or cooling surface of the heat transfer auxiliary elements 18 and / or cooling tubes 17, respectively, results in a reduction in the heat exchange capacity of the device. If, on the other hand, the heat transfer power is to be increased, then liquid metal from the reservoir 7 is supplied to the heat transfer auxiliary elements 18. This is done by opening the valves 9a and 1D with the valve 12 closed so that the heat transfer auxiliary elements 18 located below. Liquid metal refilling can also be accomplished by pressure using a suitable pressure source.

The on-line decoking process of the liquid-metal liquid is completely drained from the heat transfer auxiliary elements 18 so that there is practically no heat transfer from the heat transfer auxiliary element plate bodies 18 to the cooling tubes. Thereafter, the heat transfer auxiliary elements 18 are heated by steam or a mixture of water vapor and air, such that gasification or combustion of the petroleum coke deposited on the heated surfaces of the heat transfer auxiliary elements 18 occurs. The cooling water remains in the cooling tubes, which are thus kept at a low temperature. The plate bodies of the heat transfer auxiliary elements 18 that are exposed to high temperatures are preferably made of heat-resistant alloys.

On the other hand, the cooling tubes 17 can be made of carbon steel or low-alloy material.

In the embodiment of Figures 6 and 7, the heat transfer auxiliary elements 18 consist of tubes 39 of heat-resistant material which are surrounded by water cooling tubes and are welded at both ends with hemispherical chambers 31 and 32. The liquid metal here fills - an annulus between the tubes 17 and 30 and hollow spaces in the chambers at both ends.

8 and 9, the cooling tubes 17 are formed as fixed tubes consisting of a jacket tube 34 and an inner tube 35. The heat transfer auxiliary elements 18, as in the embodiment of FIGS. 6 and 7, are formed of tubes 30. At the other end, they are connected to the collector 36 and the liquid metal outlet pipe 6 by means of a connecting pipe 39 and a collecting pipe 40. The cooling water flows into the inlet pipes 17 via a manifold 37 which is connected to the inner pipe 35. The water vapor / water mixture then flows through the annular gap between the pipes 34 and 35 into the collector 36 and flows through the outlet throat 38. By this embodiment eliminate problems arising. with thermal expansion without the use of compensators or similar auxiliary devices.

In the embodiment according to item 10, it is a boiler-type boiler consisting of boiler tubes 41 which are welded at both ends to the base plate 42 and 43. In the boiler tubes 41 there are inserted tubes 44 of heat-resistant material through which flue gases pass. while serving as auxiliary elements for heat transfer.

Claims (8)

SUBJECT A method of heat exchange, in particular for the cooling of fissile gases, wherein the flowing heat transfer medium transfers its heat to another flowing heat transfer medium by means of an auxiliary medium, characterized in that the heat exchange power is controlled by changing the filling state of the auxiliary heat transfer medium. 2. A method according to claim 1, characterized in that a liquid metal is used as the auxiliary heat transfer medium. 3. Method according to claim 1, characterized in that the auxiliary medium is pumped off by means of pressure and admitted by a natural gradient. 4. Apparatus for carrying out the method according to Claims 1 to 3, comprising a heat exchanger consisting of heat transfer tubes overflowing or flowing through one heat transfer medium and surrounded by external or internal heat transfer elements which are flowing through or flow through another heat transfer medium and are provided with auxiliary charge The boiler tubes 41 and the smoke tubes 44 are connected to each other by welded flanges 45 and 46 and compensators 47 and the space between the two tubes is filled with liquid metal as a heat transfer auxiliary medium. The liquid metal can be supplied and discharged through the orifices 48 and 49. The auxiliary elements 18 " are formed as in the embodiment of FIGS. 4 and 5, the heating surface on the inner pipe side and the cooling surface on the outer pipe side. The proposed heat exchange method or the proposed device for carrying out this method can be used not only as a cooler but also as a steam generator whose power can be controlled by changing the state of the liquid metal working charge in the auxiliary elements 18, 18 ', 18' and 18 ' For heat transfer. The proposed device according to the invention can be used as a controllable heat exchanger for any combination of media and any direction of heat flow. Solenoid valves or similar controls can be used to control the charge level. The gas flow can also be in the opposite direction, i. from the bottom up, without changing the procedure. The invention is characterized in that the heat transfer auxiliary elements (18, 18 ', 18 ", 18'") are connected to the auxiliary medium reservoir (7) via the inlet and outlet valves (9, 10) to change the state of their charge. . Device according to claim 4, characterized in that the heat transfer auxiliary elements (18, 18 ', 18 ", 18'") are connectable to the pressure source (13) and the auxiliary medium reservoir (7) is positioned higher than the auxiliary heat transfer elements (18, 18 *, 18 ", 18 '"). Device according to Claims 4 and 5, characterized in that the heat transfer tubes (17) are arranged in rows which are each surrounded by one plate-shaped auxiliary heat transfer element (18). Device according to Claims 4 and 5, characterized in that each heat exchange tube (17, 41) is surrounded by a coaxial auxiliary element (18 ‘, 18,, 18‘)) for heat transfer, tubular in shape. Device according to Claims 4 to 7, characterized in that the heat exchange tubes (17) are designed as fixed tubes.