CH616740A5 - Liquefier in tubular-boiler construction - Google Patents

Description

The present invention now relates to a new type of liquefier, which enables an arbitrarily high yield without risk of explosion and without the disadvantages of the above-mentioned methods and apparatus. The condenser in tube design, according to the invention, is characterized in that, in addition to the actual heat exchange tubes for liquefaction, which are supplied from the outside by a cooling liquid, e.g. B. evaporating refrigerant, are surrounded and cooled, at least one downpipe, one or more liquid overflows and gas inlet openings, for. B. gas injection nozzles, to the individual liquefaction heat exchange tubes. In operation, the condenser is filled with condensate to a little above the upper tube plate, while the gas to be liquefied is blown through the nozzles under the heat exchange tubes, so that a buoyancy arises, which in turn leads the condensate-gas mixture through the

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Heat exchange tubes conveyed upwards at such a high speed that strong turbulence and a correspondingly high heat transfer from the condensate to the tube wall is generated.

The invention is explained in more detail below with reference to FIG. 5, in which the accompanying drawings

Fig. 1 is a schematic sectional drawing through a preferred embodiment of a liquefier for hydrogen-containing chlorine gas, and

2 shows a schematic sectional drawing through a further embodiment of a condenser equipped with an additional heat exchanger.

As can be seen from Fig. 1, the condenser is essentially a vertical tubular boiler apparatus. In addition to the actual heat exchange tubes for liquefaction 1, the 15 from the outside by a cooling liquid A, z. B. evaporating refrigerant, surrounded and cooled, it has at least one downpipe 2, a liquid overflow 3 and directly below the individual condensing heat exchange tubes, gas injectors 4 arranged coaxially with the same filled with liquid chlorine. The gas B to be liquefied is blown through the nozzles 4 immediately below the lower inlet of the heat exchange tubes 1, so that it mixes with the liquid chlorine, distributed in small bubbles. In a similar way to the known mammoth pumps, this creates a buoyancy which conveys the mixture upwards at high speed through the heat exchange tubes 1, as a result of which there is strong turbulence and a correspondingly high heat transfer on the tube wall. During the ascent, the corresponding chlorine fraction can condense from the vapor bubbles, which in turn reach the surface with a high hydrogen content and minimal individual volume and can escape as residual gas from the liquid into the gas space 6 35, which is kept as small as possible. Here, the residual gas C by metering an inert gas, for. B. Air or nitrogen D can be diluted so far that the explosion limit is not reached. The liquid E freed from the bubbles returns through the downpipe 2 to the lower space of the condenser, where it flows back to the condensation pipes at a low speed, with any solid impurities generally settling on the floor. The excess liquid E created by the condensation can flow out through the overflow.

As can be seen from the above description, the condenser according to the invention completely eliminates the risk of an explosion with an arbitrarily high volatilization yield, even in the case of harmless mini-explosions which may occur within individual bubbles. In addition, the described forced circulation of the vapor / liquid mixture in the heat exchange tubes enables a significant increase in the heat transfer, so that, with the correct dimensions, this can considerably exceed that of the conventional tubular boiler heat exchangers. 55

The condenser, according to the invention, can advantageously be supplemented by a heat exchanger (see FIG. 2), e.g. B. a sprinkler tower 7 with Raschig ring filling, in which chlorine gas B is brought into direct contact with the supercooled liquid chlorine E ® originating from the condenser, by the liquid chlorine E flowing out through the overflow 3 and then through a gas barrier 8,

whereupon the Raschig rings in sprinkler tower 7

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is tested. By exchanging heat between the two phases, chlorine can condense from the gas while the liquid warms up to saturation temperature, which can improve the utilization of cooling energy.

The invention has been described here, as in the following example, with particular attention to the production of liquid chlorine from hydrogen-containing chlorine gas. However, it goes without saying that the liquefier according to the invention can be used and is equally suitable for all gas mixtures which behave similarly.

example

A raw gas that is compressed to a pressure of 2.5 kg / cm2 and out

98.7 Vol.-0 / o Cl2 0.6 Vol.-o / o CO2 0.4 V0I.-0/0 H2 0.3 V0I.-0/0 Na + 02, is with a yield of 99 % liquefy.

1) In the liquefier according to FIG. 1, the gas mixture flowing in in its original composition gradually loses chlorine content through condensation until it has the residual gas composition of 43.2% by volume of CI2, 26.2% by volume / o CO2, 21.9 Vol .-% H2 and 8.7 Vol.- ° / o Na + O2 reached. The static pressure of the liquid column and the flow resistance must be overcome so that the gas pressure is reduced by 0.6 kg / cm2 to 1.9 kg / cm2. According to these values, the liquefaction of the chlorine begins at a temperature of -12.4 ° C and ends at a temperature of -29.7 ° C with 99% of the original chlorine content as condensate. After leaving the liquid, the residual gas is diluted with air to such an extent that the explosive H2 concentration is not reached.

b) The same gas mixture is liquefied in a conventional tubular boiler apparatus, whereby it must be diluted with the amount of air required to fall below the explosion limit before it enters the liquefier, resulting in the following initial composition:

91.57 V0I.-0/0 CI2 0.56 Vol.-o / o COa 0.37 V0I.-0/0 H2 7.5 Vol.-o / o Na + Oa

With the same yield of 99% as calculated in a), the residual gas consists of 21.35% by volume Cl2, 5.22% by volume CO2, 3.46% by volume H2 and 69.08% by volume. % N2! + O2. Its final pressure, taking into account a flow resistance in the condenser of 0.2 kg / cm2, is 2.3 kg / cm2. The initial pressure is the same as in a), 2.5 kg / cm2.

These values result in a chlorine liquefaction temperature of -14.5 ° C at the beginning and - 49.5 ° Celsius at the end of the liquefaction process.

The arithmetic mean temperature difference is generally used to dimension this type of heat exchanger. This comes at an evaporation temperature of the refrigerant used for cooling of -50.8 ° Celsius for the condenser according to the invention to 29.8 ° C and for the conventional tube boiler condenser to 18.7 ° C. Assuming that the heat transfer coefficients are the same in both cases, the heat exchange area required for the same liquefaction capacity, and thus also the apparatus itself, must be 59 ° / o larger for the conventional condenser b).

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2 sheets of drawings

Claims (2)

616740 PATENT CLAIMS 1. The simplest method is to the raw gas before entering the condenser - usually a tubular boiler heat exchanger, cooled by a suitable cooling medium - in which the high hydrogen concentration can occur, a corresponding amount of inert gas, for. As air or possibly nitrogen, admix, whereby the concentration of the. Even with high yield of chlorine Hydrogen in the exhaust gas remains below the explosion limit. This process has the disadvantage that, due to the reduced partial pressure of chlorine, the liquefaction temperature is lower than without the addition of inert gas. In addition, the heat transfer is significantly deteriorated by the presence of the non-condensable gases. 1 for the liquefaction of gases, characterized in that the liquefier is filled with condensate during operation up to a little above the upper tube sheet, while the gas to be liquefied is blown through the gas inlet openings under the heat exchange tubes, so that a buoyancy arises, which in turn causes the mixture of Condensate and gas are conveyed upwards through the heat exchange pipes at such a high speed that strong turbulence and a correspondingly high heat transfer from the condensate to the pipe wall is generated. 5. Use according to claim 4 for the production of liquid chlorine from hydrogen-containing raw gas, characterized in that the condensation of hydrogen-containing chlorine which is blown through the gas inlet openings takes place in the vapor bubbles during the ascent in the heat exchange tubes, and that the residual gas with a high hydrogen content immediately when the bubbles emerge from the liquid through inert gas, e.g. B. Air or nitrogen, as far as diluted that the hydrogen concentration is below the explosion limit. When producing or extracting pure chlorine, one of the usual methods is to break down common salt into the components by electrolysis, to dry and filter the chlorine gas thus produced, and then to liquefy it. As a result, chlorine is obtained in a largely pure form, i.e. H. also freed from the accompanying gases, such as oxygen, carbon dioxide and hydrogen, which are unavoidable during electrolysis. For reasons of economy and also with regard to environmental protection, the highest possible yield, i. H. the lowest possible chlorine content of the exhaust gas released from the liquefier into the atmosphere. As a result, however, the percentage composition of the exhaust gas is shifted in the sense that the proportion of hydrogen becomes larger, so that an explosive gas mixture can be produced if the amount is correspondingly high. In order to avoid the risk of an explosion or to keep the effects under control, even with chlorine liquefaction plants with a high yield, z. For example, the following methods have been developed: 1.Condenser in tubular boiler design, characterized in that, in addition to the actual heat exchange tubes for liquefaction, which are surrounded and cooled by a cooling liquid from the outside, it has at least one downpipe, one or more liquid overflows and gas inlet openings to the individual liquefaction heat exchange tubes . 2. A condenser according to claim 1, characterized in that the gas inlet openings are gas injection nozzles. 3 condenser according to claim 1 or 2, characterized in that it has an additional heat exchanger, expediently a sprinkler tower, in which at least part of the supercooling heat of the condensate produced is used for precooling the gas to be condensed or for its precondensation and thus the utilization of the cooling energy is improved. 4. Use of the condenser according to claim 2. Another way of preventing the explosive hydrogen chlorine reaction, or at best restricting it to harmless minimal explosions, is to distribute the explosive mixture into very small, separate quantities and at the same time ensure that the heat of reaction that arises is immediate is dissipated. Known condensers based on this principle are e.g. B .: (a) Bubble columns With these bubble columns, the gas to be liquefied enters the bottom of a container that is filled with liquid chlorine up to a certain height. During their ascent in the externally cooled liquid, the individual gas bubbles lose most of the chlorine content through condensation in the liquid. As the chlorine content decreases, the hydrogen concentration in the bubbles increases, which in turn decreases in volume according to the condensed chlorine. Even in the event of explosive chlorine-hydrogen reactions in the individual small bubbles, the heat generated is immediately absorbed by the surrounding cold liquid, thus preventing the propagation of the reaction. The disadvantage of this device is the rather poor heat transfer when cooling the almost static chlorine liquid. In addition, it is also difficult to accommodate the necessary heat exchange surface for larger capacities without disproportionately increasing the content or the height of the bubble column, (b) chlorine liquefier with very small liquefaction rooms (see e.g. DT-PS 1 056 155) In these devices, the cooled heat exchange surface for chlorine condensation is designed in such a way that very narrow channels are formed, as a result of which the same effect is achieved as in the bubble columns, namely that only small amounts of gas can explode at once, and here too the resulting one Heat is dissipated through the surrounding surfaces and the propagation of the reaction is prevented. The disadvantage of this method is also the poor heat transfer and also the relatively high price of the device. In both devices, the necessary amount of diluting air is added to the residual gas obtained immediately after leaving the liquid or the liquefaction channels before the gas mixture is discharged as exhaust gas from the device. However, this dilution no longer affects the yield.