US2157318A

US2157318A - Process of cooling gases

Info

Publication number: US2157318A
Application number: US120911A
Authority: US
Inventors: Baehr Hans; Braus Karl
Original assignee: IG Farbenindustrie AG
Current assignee: IG Farbenindustrie AG
Priority date: 1936-01-24
Filing date: 1937-01-16
Publication date: 1939-05-09
Anticipated expiration: 1956-05-09

Description

May 9, 1939. H BAEHR E AL 2,157,318

I PROCESS OF COOLING GASES Filed Jan. 16, 1937 Hans Baehr Karl Braus INVENTORS THEIR ATTORNEYS- Patented May 9, 1939 UNITED STATES PATENT OFFICE PROCESS OF COOLING GASES Hans Baehrand Karl Braus, Leuna, Germany, assignors to '1. v(l. Farbenlndustrie Aktiengesellschaft, Frankfort-on-the-Main, Germany Application .lanuary 16, 1937, Serial No. 120,911 In Germany January 24, 1930 Claim!- (Cl. 62-176) The present invention relates to a process of cooling Bases.

.A method frequently used to cool hot gases or vapors consists in causingatomized water or an- 5 other liquid to evaporate in the gasesi This method of working succeeds with comparative easiness if thecooling temperature to be attained lies considerably above the boiling point of the evaporating agent. Dimculties, however, arise .10 when the gases have to be cooled down to a temare suchas to exclude the use of the simple injection method forthe cooling of gases in many cases which has therefore to be done by complicated indirect processes. For example, if the gases to be cooled contain constituents which are liable, in the presence of liquid water, to attack the structural materials of the apparatus, as is the case for example with gases obtained by roasting pyrites, care must be taken that no liquid water separates at any place of the apparatus as otherwise the structural materials would be destroyed. The injection water. also, if introduced between twois'uperimposed contact layers, must be completely evaporated, also in view of the fact that it would otherwise hit the lowermost layer and damage the same. The separation of liquid water must finally be avoided in all cases where 40 products are to be recovered from the gases at the desired cooling temperature which products would solidify at still lower temperatures, as for example at 100 C., and then clog the separator. We have now found that the liquids used for cooling gases or vapors or mixtures thereof by the injection method can be rapidly and completely vaporized if the same (preferably water) have a boiling temperature under the actual gas pressures below the gas temperature to be obtained by the cooling, and are released from pressure while in a finely distributed state, into the medium to be cooled at a temperature above their boiling temperature under the pressure of the gases to be cooled but below the temperature of 06 these gases.

In order to atomize the injection liquid which is usually done [by forcing it through narrow nozzles, it mustbe subjected to an elevated pressure, and therefore it is possible in general to heat the liquid, as for example water, to temperatures above the boiling point corresponding "to the pressure of the gas. Where injection nozzles are used, the water supply conduit of which is under no or only too small a superatmospheric pressure, the necessary pressure must be produced by the arrangement directly in front of the nozzles of a throttling valve or an,- other throttle.

The water may be heated in any appropriate manner, 1. e. either indirectly by means of steam or flue gases or directly by leading steam into the water contained in a suitable mixing device.

If the injection is to be performed within the reach of a boiler, the superheated pressure water wanted is generally available in the form of the feed water or the boiler water itself. When special heating devices are used, these are preferably arranged closeto the place where the injction is performed, to avoid any loss in temperature after superheating as muchas possible.

When cooling gases or vapors under ordinary pressure it is usually sufilcient that the water to be vaporized supplied to the injection nozzles has a temperature above C., preferably at least C., to C. Whereas higher temperatures merely require somewhat larger amounts of water to be vaporized, the lowering of the temperature,

to below the boiling temperature of the injection wat'er immediately eifects such a slackening of the speed of evaporation that it is no longer possible to cool the gases to low temperatures, more particularly below 200 C.

If the gases to be cooled are under'pressure, higher temperatures of the water must be maintained in accordance with the pressure of the gas. On the other hand, however, when cooling gases under a pressure inferior to atmospheric pressure water temperatures of less than 100 C. may be used; In each case the temperature of the liquid under pressure should be some degrees centrigrade above the boiling point at the actual gas pressure; preferably this difference should at the least be about 5 C.

The present invention is not restricted to the use of water, but it is practicable quite generally in the case of any liquids which are vaporized in gases or vapors for the purpose of cooling gases and do not exert any other undesired influence on these gases.

In carrying out the process according to this invention it is advantageous to assist the vaporization for example by using atomizing nozzles producing the finest possible degree of atomization, arranging a plurality of nozzles, atomizing towards various directions within the vaporizer or other well known means.

The aflixed drawing is a diagrammatic illustration of an apparatus wherein the present process may be carried out.

Referring to this drawing, the hot gases enter cooling chamber I through opening 2 and leave through exit 3. Pipe 4, located in the upper part of cooling chamber 1, is provided with spraying nozzles 5. Pump 6 is used to build up the pressure of the cooling medium, which flows through pipe I, into and through heater 8, and from there to cooling chamber I through pipe l0. Steam enters heater 8 through pipe 9 and the resulting condensate leaves the heater through pipe ll. Thus, for instance, if hot gases entering opening 2 at a temperature of 400 C. are to leave cooling chamber i at a temperature of 150 C. and pump 6 is adjusted so as to maintain a water pressure of about 10 atmospheres in the pipe line, the quantity of steam entering heater 8 is regulated so that the water passing through heater 8 will leave the heater at a temperature of 140 C. When this water is forced through spraying nozzles in cooling chamber i, it is so quickly and completely vaporized that no water is col-.

lected at the bottom I! of the chamber and that no droplets of water are carried out with the gases which have been cooled to 150 C.

The process will be used with advantage in any case where gases and vapors shall rapidly and within a narrow space be cooled down to low temperatures without any separation of the injected liquid. It is excellently adapted for use in exothermic catalytic reactions, in which the main part of the gases or vapors involved is converted by means of a first contact layer, whereas the final conversion is effected by means of a second contact layer and in which the gases or vapors are cooled between the said two stages. Processes of the said kind are applied forexample for producing hydrogen and carbon monoxide from hydrocarbons and steam or for oxidizing sulphur dioxide to sulphur trioxide, in the synthesis of ammonia from nitrogen and hydrogen, liquefied ammonia being preferably injected in this case between the contact layers for cooling the gas, or in the synthesis of hydrocarbons from carbon monoxide and hydrogen, superheated hydrocarbons being preferably injected in this latter case between several contact layers. The process is valuable also when products formed are to be precluded from decomposition by cooling them rapidly, as for example in the production of nitrogen oxides by combustion of ammonia in the production of unsaturated hydrocarbons by thermal decomposition and other cases. A special importance of this process resides in the possibility of cooling such gases by the injection of water which, as for example gases obtained by roasting pyrites contain substances which are aggressive in the presence of water and with which the formation of liquid water must therefore be carefully avoided.

The speed oi evaporation of the water in the said method of working is so high that the process is even applicable for cooling 8 mixtures which, as for example the sulphur containing gases obtained by the well known Claus process, consist of substances, in the latter case of sulph which would immediately solidify when cold I water would be injected. Said Claus process comprises the catalytic oxidation of hydrogen sulfide at high temperatures with air according to the equation and thereby gives rise to gases of relatively high temperatures between about 200 and 500 C. which contain substantial quantities of elemental sulfur. when cooling these gases in accordance with the present invention, there is no danger of solidifying the sulfur as has heretofore been the case. The present process is, therefore, of great advantage for use in the production of sulfur by the Claus process and its modifications.

The present invention, however, is not confined to the cooling down ,to low temperatures alone. It may be employed with the same result in order to obtain any desired gas temperature. For example, if the injected water or other liquid would be vaporized at higher temperatures also without being superheated, the superheating accelerates the vaporization to such an extent that the dimensions of the Vaporizers may be strongly reduced and considerable savings in apparatus may be realized.

The following example serves to illustrate how the present invention may be carried out in practice, but the invention is not restricted to this example.

Example 10,000 cubic meters per hour of Claus furnace contact gases having a temperature of 400 C. and containing 110 grams of sulphur per cubic meter (measured at 400 C.) are to be cooled down to 150 C. for the purpose of converting the gaseous sulphur into the liquid phase in order to separate it. The said gases are led downwards through a cylindrical vaporizer having 3 meters in diameter and 4 meters in height. At the top of the vaporizer 3 water supply pipes are introduced radially and in a symmetrical order. Each of the said pipes which extend nearly to the center of the vaporizer, has screwed on thereto at equal intervals 6 atomizer nozzles with a spraying aperture of 0.9 millimeter width, the said nozzles being so arranged in a downward direction that their central lines deviate from the vertical direction by an angle of 30 either to the right or to the left. Before their arrangement all of the nozzles are carefully adjusted so as to ensure the finest possible atomization of the water. Through the said nozzles 900 liters of water are injected per hour into the vaporizer with a temperature of about 125 C.

The injected water is completely vaporized in the vaporizing space. The gases leaving the vaporizer at the bottom above the vaporizer sump are cooled down to 150 0., the whole of the sulphur which was previously in the gaseous state being condensed into the liquid phase. One third of the sulphur precipitates as a liquid in the vaporizer sump and is continuously withdrawn therefrom by means of a heated overflow pipe; the bulk of the sulphur is practically completely separated on an electro-filter arranged behind the cooler.

If the injection water is atomized at a temperature of 90 instead of 125 C. the other conditions remaining unchanged, the gases leaving the vaporizer still have a temperature of 250 C.-, so that a considerable part of the sulphur remains in the gaseous phase and cannot be completely recovered by means of the electro-filter. Moreover. the water which has not been vaporized collects in the vaporizer sump and there causes the sulphur to solidify which in turn leads to incrustations and stoppages, so that neither the complete recovery of the sulphur nor a regular operation is possible.

What we claim is:

l. A process of cooling a hot gaseous medium by injecting and evaporating a liquid therein comprising injecting the said liquid in a finely distributed state and at a temperature above its boiling temperature corresponding to the pressure of the gaseous medium to be cooled and belowthe temperature of the said gaseous me dium, the quantity of said liquid being so limited that the liquid is completely evaporated.

'2. A process of cooling a hot gaseous medium by injecting and evaporating water therein.comprising injecting the said. water in a finely distributed state and at a temperature above its boiling temperature corresponding to the pres-' sure of the gaseous medium to be cooled and below the temperature of the said medium, the quantity of said water being so limited that the water is completely evaporated.

' 3.- A process of cooling a hot gaseous medium by injecting and evaporating water therein comprising injecting the said water in a finely distributed state and at a. temperature which-is at least about 5 C. above its boiling temperature at the pressure of the medium to be cooled and below the temperature of the said medium, the quantity of said water being so limited that the water is completely evaporated.

,4. A process of cooling a hot gaseous medium under atmospheric pressure and having a temperature between about 200 C. and 500 C. by injecting and evaporating water therein comprising injecting the said water in a finely distributed state and at a temperature between about 105 and 130 0., the quantity of said water. being so limited that the water is completely evaporated.

5. A process of cooling hot gases under atmospheric pressure obtained by the well known Claus process and its modifications, having a temperature between about 200 and 500 C. and containing substantial amounts of elementary sulphur by injecting and evaporating water therein comprising injecting the said water in a finely distributed state and at a temperature of about 125 0., the quantity of said water being so limited that the water is completely evaporated.

I HANS BAEHR. KARL BRAUS.