DE2055059A1 - Method and device for cooling soot-containing gases - Google Patents

Description

Shell Internationale Research Maatschappij N.V., The Hague, Netherlands

¹¹ Method and device for cooling dimensionally stable gases "

Priority: November 11, 1969, Netherlands registration no. : 69 16 941

The invention relates to a method for cooling soot-containing gases that result from the partial combustion of hydrocarbons develop. It also relates to an apparatus for performing this method.

When cooling hot gases that result from partial combustion The use of hydrocarbons inevitably produces soot Contained in the form of dry particles, result both from the temperatures occurring and from the soot Problems as explained below. If such gases are passed through helical pipes, the their outside are cooled by a coolant, takes .the wall of the pipe coil as a result of the heat transfer

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high temperature.

When twisting a straight tube into a helical one Coiled pipes present out-of-roundness and irregularities . the wall thickness, which leads to the strength of the helical Pipe coil is smaller than that of the originally straight pipe. The temperature problem mentioned is with this one connected to health. As a result of the heat transfer can namely the temperature of the pipe coil wall rise to such a high value that it is reduced as a result of the unhealth and the reduced Strength of the coil leads to a collapse of the coil if the pressure of the coolant is significantly higher than that of the gas to be cooled.

The heat transfer increases with increasing gas velocity, which has the consequence that the temperature of the pipe wall increases. At the same time, an increased gas velocity leads to a shorter residence time of the gas in the helical pipe coil, which results in a relatively small temperature drop in the gas. Now \ A too high wall temperature results in that the gas velocity must be lowered, whereby the Gasendtemperatur due to the reduced residence time also drops. On the other hand, increasing the gas velocity increases the risk of soot being deposited on the inner wall of the pipe ^ and after a thin layer of soot has been deposited, the heat transfer decreases, with the temperature of the pipe wall dropping even further (which is of less importance if the pipe wall is sufficiently strong \ and the gas

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end temperature rises again. When the gas velocity is increased, the thickness of the deposited soot layer on the inside of the pipe wall can decrease and even disappear completely, whereby the heat transfer is considerably improved, but the pipe wall can reach an impermissibly high temperature and, as a result of the change in heat transfer, no more uniform cooling of the gas takes place. It is therefore impossible to deal with the temperature problem and the soot deposition problem independently. These problems occur, for example, in the production of hydrogen- ^{carbon en- 1} ^ oxyd-Gemi (synthesis gas) by partial combustion of hydrocarbons and the subsequent cooling of the synthesis gas, and they must be supplied to a solution.

It has now been found that the use of helical Pipes for cooling the gas ensure a uniform and safe cooling process if the gases are in front of their entry in the helical coil are partially cooled by passing them through a straight pipe, at the same time certain conditions must be met.

The invention accordingly relates to a method for cooling soot-containing gases formed during the partial combustion of hydrocarbons in helical pipe coils, which is characterized in that the gases are passed through a straight pipe or several straight pipes with a throughput of at least 100 kg / m and at a temperature of. 1200 ⁰ G or below are cooled, whereupon the gases are further cooled

by going through one or more helical coils are passed, of which at least one extends essentially in the direction of the straight pipe or the straight Extends tubes, the straight tube or tubes through a coolant in cocurrent with the in the tube or in the Pipes flowing gases is or are cooled.

Choosing a straight pipe to cool the gases down to one

Temperature of 1200 ⁰ C or below is not obvious, as it is known int, -3H for soot in a straight pipe more quickly

deposited than in a helical coil.

The cooling of the gases in the straight pipe or in the straight pipes to a temperature below 1000 ^° C. is not necessary within the scope of the invention.

The synthesis gas, which is produced through partial combustion of hydrocarbons, has an outlet temperature of 1300 to 1400 ^° C. when it leaves the reactor. If water is used as a coolant, steam is produced during the cooling process.

Part of the steam can be used as an auxiliary medium in the partial combustion of the hydrocarbons. As a rule, steam is used as an energy source, for example as high-pressure steam for generating electricity. In this case, steam with a pressure of 50 to 150 atm is preferred. The invention is of particular importance for the generation of such vapor pressures because, at the pressures mentioned, relatively high pipe wall temperatures occur and a relatively high one

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Pressure is exerted on the pipe wall, especially if it is desired for reasons of process management, the gas pressure considerably lower than the vapor pressure. When according to the invention Processes higher overpressures can be permitted than in a process in which only helical coils are used to cool the gas.

The cooling of the gases depends on the heat transfer and the Residence time of the gases in the pipes. The heat transfer in turn depends on the throughput (or the mass velocity) of the gases, whereas the residence time depends on the throughput (or the mass velocity) and the length of the straight pipe.

To cool the gases to a temperature of 1200 ^° C. or below, it is usually sufficient to use a straight pipe with a length of about 2 m. If an increase in heat transfer is desired, the gas velocity can be increased and the tube made longer than 2 m if this is necessary to achieve a sufficiently long residence time. \ It is of course possible to use several straight pipes that are arranged parallel to each other and each of which is connected to a helical pipe coil.

The length of the straight pipe can be chosen up to 10 m. Usually, however, such a length is used because of the resulting Height of the heat exchanger avoided, and the pipe length is preferably kept smaller by using a plurality of tubes arranged in parallel, each of which 'is connected to a helical coil.

10 98 21/18 0 8 original, nopegted

Preferably at least some of the consecutive ones extend Windings of the helical pipe coil at least substantially in the direction of the straight pipe. With regard the available space can make the longitudinal axis of the coil at a small angle with the extension of the longitudinal axis of the straight line Include pipe. The connection of the straight pipe with a helical pipe coil can be done in such a way, that the longitudinal axis of the coil at least substantially lies in the extension of the longitudinal axis of the straight pipe, or so that the longitudinal axis of the pipe coil is at least runs essentially parallel to the extension of the longitudinal axis of the straight tube. The helical pipe coil can, if so desired, consist of two parts, the arrangement can be made so that the first part is in Direction of the straight tube extends and is connected to a second part, the turns of which about the same longitudinal axis are arranged, but different radial distances with respect to

^ borrowed this longitudinal axis, this second part being within or is arranged outside, preferably inside, of the first part. This way, two become concentric helical coils formed.

The throughput (the mass velocity) of the gases is selected as a function of the soot deposit and the permissible pipe wall temperature. The throughput is preferably at most 500 kg / m .Bee, because with a larger throughput the pipe wall temperature θο can become high, the fact that its resistance to the erosive attack of the soot particles quickly decreases.

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takes. The throughput when the gases enter the pipe is

preferably in the order of magnitude of 200 to 350 kg / m .see chosen.

At high vapor pressures, e.g. 80 atm or more, the length of the straight pipe is preferably greater than 2 m, e.g. 4 to 6 m is selected, in which case the throughput is 200 to

350 kg / m .see is.

The cooling liquid is introduced into the heat exchanger in such a way that the straight pipe or pipes are cooled in cocurrent with the gases flowing through the pipe or pipes. In this case, at least part of the cooling liquid evaporates and the coolant cools, if water is used in addition to the coolant consisting of a water-steam mixture, also the helical pipe coils, with steam being formed again. In this case (with regard to the throughput and the turbulence of the coolant) it is advantageous if it is ensured that the free flow cross-sectional area of the space accommodating the straight pipes is preferably at most 30 ia of the cross-sectional area of the space accommodating the helical pipe coils j. In order also in cases where the \

free flow cross-sectional area is greater than 30 #, a { To ensure proper guidance of the coolant, baffle plates can be used in which the straight pipe or the straight tubes receiving space are arranged. When using four straight tubes, these baffles can the Have the shape of a curved shield and are symmetrically shaped

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be arranged along the wall of the room, the concave sides the shields are directed against the wall.

The invention also relates to a for generating synthesis gas Serving process, which is characterized in that the gases contain up to 5 wt. $ soot and in the partial combustion of hydrocarbons, which may contain soot, by means of oxygen or with oxygen enriched air, with or without steam supply, at superatmospheric pressure, preferably between 5 and 150 atm, generated v / earth; the resulting gas mixture is cooled in the manner explained above. The invention relates focuses specifically on a process in which gases containing soot are reduced to a final temperature of 260 to 340 C, steam with a pressure of 50 to 150 atm is obtained. The vapor pressure can be on any Value can be set in this range, depending on the purpose of the high-pressure steam.

Another object of the invention is a heat exchanger for cooling in the partial combustion of hydrocarbon

soot-containing gases produced by substances, which are characterized by this is that it has a>

straight pipe or several straight pipes with a minimum length of 2 m, one or more connected to a gas outlet helical coil-η, a coolant supply line and has a coolant discharge line, wherein the coolant supply line is designed so that the coolant to the'Gas -

ORIGINAL INSPECTEO 109821/1808

inlet end of the straight pipe ″ or the straight pipes flows, and wherein the helical coil or the helical Coiled tubes are connected to the straight tube or straight tubes and at least a few turns each helical pipe coil extend at least substantially in the direction of the associated straight pipe.

Another object of the invention is a device for generating a gas mixture containing hydrogen and carbon monoxide, which has a reaction chamber for the tf ^J ? Wise combustion of hydrocarbons by means of oxygen, this chamber optionally with steam under superatmospheric pressure, in particular between 5 and 150 atm, is fed, and wherein a heat exchanger is connected to the outlet of the reaction chamber, which has the structure explained above.

The invention is explained in more detail below using exemplary embodiments with reference to the drawings.

Fig. 1 is a schematic view of an apparatus for partial burning of hydrocarbons and for cooling the resulting gases;

Pig. Figure 2 is a schematic view of an embodiment of a heat exchanger according to the invention;

3 is a cross-section through another embodiment of the heat exchanger, the section being taken through the space receiving the straight tubes, and the heat exchanger having four straight tubes and four helical tube

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snakes as well as with baffle plates, which are in the the straight tubes receiving space are arranged.

The device shown in Fig. 1 comprises a reactor A which is equipped with a ^{fuel supply line a leading to a burner part A 1 of} the reactor and with an oxygen supply line b, while steam, if used, both through line a and through the line b can be fed. The reactor A is connected to a connection part C by a connection B. The hot gases flow through the connection B and the connection part C to a heat exchanger D, which is equipped with a straight pipe and a helical pipe coil and also an outlet c for the cooled gases, an inlet d for the coolant, e.g. water, and a Has outlet e for the coolant. The straight tube, which is at least 2 m in length, is denoted by f and the coiled tube is denoted by g.

Fig. 2 shows a partial longitudinal section through an embodiment of the heat exchanger. The heat exchanger consists essentially of a cylindrical housing 13 with a Base plate 3, which rests on the connection part 5, to which a gas supply line 4 is connected. The heat exchanger furthermore has outlets 8 and 9 for the cooled gas, a coolant supply line provided at its lower end with spray nozzles 11 10 and helical pipe coils 6 and: 7, which are connected to straight pipes 1 and 2, which at least

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at least 2 in long. The coolant, generally water, is fed through the line 10 and sprayed through the spray nozzles 11 against the base plate 3, from which it is subsequently rises upwards and thereby the straight tubes 1 and 2 and the helical tube coils 6 and 7 cools. The helical ones Coils 6 and 7 are in one through the wall of the supply line 10 and the wall of the cylindrical housing 13 formed annular space. The coils 6 and 7 have a common longitudinal axis which coincides with the longitudinal axis of the supply line 10. The heat exchanger is also equipped with two baffle plates for the cooling water, which extend from the base plate essentially to that point, at which the helical tube coils are connected to the straight tubes. The arrangement of these baffles is not shown in the drawing.

FIG. 3 shows a cross section through the space receiving the straight tubes of an embodiment of the heat exchanger according to FIG. 2, which is equipped with four helical tubes which are connected to four straight tubes. The cross-section shows the baffle plates for the coolant, the four straight pipes and the coolant supply line. The straight tubes 20, 21, 22 and 23 are arranged in the space 26 delimited on the inside by the coolant supply line 24 and on the outside by the housing 25 of the heat exchanger. Shield-shaped baffle plates 27, 28, 29 and 30 for the coolant protrude into the space 26 receiving the tubes 20 to 23; Housing 25 are attached .

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Claims (1)

- 12 - Patent claims: Process for cooling soot-containing gases that are used in the '' partial combustion of hydrocarbons occurs, characterized in that the gases with a throughput of at least 100 kg / m .see through a straight pipe or several straight pipes and thereby ^{cooled to a temperature of 1200 0} C or below, whereupon the gases are further cooled by passing them through one or more helical pipe coils are conducted, of which at least one extends substantially in the direction of the straight pipe or pipes, the straight pipe or pipes being cooled by a coolant in cocurrent with the gases flowing in the pipe or pipes . will. 2. The method according to claim 1, characterized in that the longitudinal axis' of the helical coil at least substantially in the extension of the longitudinal axis of the straight Rohres lies. 3. The method according to claim 1, characterized in that the longitudinal axis of the helical pipe coil at least runs essentially parallel to the extension of the longitudinal axis of the straight tube. 4. The method according to any one of claims 1 to 3> characterized in that that the gases in the straight pipe or in the 109821/1808 straight pipes are cooled to a temperature of at most 1000 ^{° C.} 5. The method according to any one of claims 1 Ms 4, characterized in that that the gases in the straight pipe or in the straight pipes with a throughput of a maximum of 500 kg / m see to be initiated. 6. The method according to any one of claims 1 to 5, characterized in that that the ihirchsatz, 'with the' JLo gases in the straight pipe or into which straight pipes are introduced, is between 200 and 350 kg / m .see. 7. The method according to any one of claims 1 to 6, characterized in that the straight pipe or the straight pipes are cooled by the coolant near the gas inlet end of the pipe or the pipes and that the free flow cross-section sf area of the straight pipe or the space containing the straight pipes is at most 30 $> the flow cross-sectional area of the space containing the helical pipe coil or the helical pipe coils'. 8. The method according to any one of claims 1 to 7> characterized in that that the coolant causes baffle plates to flow around the straight pipe or pipes will. 9. Method according to one of Claims 1 to 8, characterized in that that the gases contain up to 5% by weight of soot 109821/1808 -H- and "in the case of partial combustion of hydrocarbons, which may contain soot, by means of oxygen or air enriched with oxygen, with or without supply of steam, at superatmospheric pressure, preferably between 5 and 150 atm. 10. The method according to any one of claims 1 to 9 »characterized in that the soot-containing gases ^{are cooled to a final temperature of 260 to 340 0} C using water as a coolant, where D .- ^ r Γ with a pressure of 50 to 150 atm er - ι will hold. ./ Heat exchanger for cooling gases containing soot resulting from the partial combustion of hydrocarbons, characterized in that, following a gas inlet, it has a straight pipe or several straight pipes with a minimum length of 2 m, one or more helical pipe coils connected to a gas outlet, a coolant supply line and a coolant discharge line, wherein the coolant supply line is designed such that the coolant flows to the gas inlet end of the straight tube or the straight tubes, and wherein the helical. Coiled pipe or coiled pipe is or are connected to the straight pipe or pipes and at least a few turns of each coiled pipe extend at least substantially in the direction of the associated straight pipe. ^: 109821/1808 '- 15 - 12o heat exchanger according to claim 11, characterized in that that the longitudinal axis of the helical coil is at least essentially in the extension of the longitudinal axis of the connected to the helical pipe coil straight tube extends. 13. Heat exchanger according to claim 11, characterized in that that the longitudinal axis of the helical coil at least essentially parallel to the extension of the longitudinal axis of the connected to the helical pipe aoulange straight pipe. 14. Heat exchanger according to one of claims 11 Ms 13, characterized in that the length of the straight tube is no more than 10 m. 15 «heat exchanger according to one of claims 11 to 14, characterized characterized in that the free flow cross-sectional area of the space accommodating the straight pipe or pipes at most 30% of the flow cross-sectional area of the helical coil or helical Coils receiving space is. 16. Heat exchanger according to one of claims 11 to 15, characterized in that in which the straight tube or the straight tubes receiving space one or more baffle plates are arranged. 109821/1808