DE3100359A1 - METHOD FOR PRODUCING AMMONIA - Google Patents

Description

DR. STEPHAN G. BESZtDES PATENT ADVOCATE

DACHAU BEL MQN _- CiIEN

POSTpf

AUTHORIZED REPRESENTATIVE AT THE EUROPEAN PATENT OFFICE

PROFESSIONAL REPRESENTATIVE ALSO BEFORE THE EUROPEAN PATENT OFFICE

MDNCHENER STRASSE 8OA Federal Republic of Germany TELEPHONE: DACHAU 4371 Postal checking account Munich (BLZ 700 100 801

Account no. 1 368 71

Bank account no.906 370 at the Kreis- und Stadtsparkasse Dachau Indersdorf (bank code 700 515 40) (VIA Bayerische Landesbank Girozentrale, Munich)

P 1 399

Claims and Description

for patent application

MONTEDISON ß.p.A,

Milano, Italy

~ concerning

Process for the production of ammonia

130049/0517

description

The invention relates to a method for producing ammonia from hydrocarbons. in the in particular, it relates to a process for the production of ammonia with the step of producing synthesis gas from hydrocarbons by reforming them with steam and oxygen.

As is well known, the reaction of hydrocarbons with steam, called primary reforming, is endothermic, while the reaction of hydrocarbons with oxygen, which is generally introduced into the process in the form of air, directly produces the nitrogen-containing synthesis mixture (3H ₂ + N ₂ ) to obtain, which reaction is called secondary reforming, is exothermic.

It is also known that ammonia is one of the mass products with a high energy content, its manufacture requires a considerable amount of energy is. It is also known that the actual energy consumption for the production of 1 kg of ammonia much higher than the stoichiometrically required theoretical Minimum consumption is, even if recovery of the heat of reaction is assumed. The relation between the theoretical value mentioned and the actual energy consumption gives the efficiency of the process at.

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The lack of energy in the world and the corresponding increase in energy costs make the problem of diminution the energy demand of the process for the production of ammonia is very noticeable.

The latest high capacity ammonia plants based on processes of steam reforming of hydrocarbons, which with integrated heat recovery cycles and with the operation of the main machines by means of Steam turbines are perfected, have an efficiency of only about 50 to 55% »which means that for Time, despite the efforts made and improvements already made, the actual energy consumption to produce 1 kg of ammonia, about twice the theoretically required minimum consumption is"

It is therefore important to try to further reduce the energy consumption in ammonia production.

The invention is therefore based on the object of providing a process for the production of ammonia from hydrocarbons, in which the energy consumption is further reduced and which therefore has a high degree of efficiency, to accomplish.

The above has surprisingly been achieved by the invention.

The invention relates to a process for the production of ammonia by generating synthesis gas from hydrocarbons through their erimary reforming

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with steam and secondary reforming of the gas mixture obtained with oxygen and downstream production of ammonia, which is characterized in that a part of the starting hydrocarbons mixed with the steam undergo a tertiary reforming, which the necessary heat is supplied by the reaction gas mixture leaving the secondary reforming is, the ammonia production under low pressure with drying of the gas supplied to it by using is carried out by molecular sieves, absorb the ammonia contained in the converted gas from water and the ammonia solution thus obtained using two at different pressures working distillation columns is distilled.

It is preferable to use a mixed type of tertiary reforming. In more detail, acts it is the type of reforming in which the reformed gas mixture that flows through within the tertiary reforming catalyst containing tubes forms, before the heat exchange takes place directly with the secondary reforming leaving gas reaction mixture, the latter of v. 3r outside of the pipes necessary for tertiary ref onnation Provides heat, is mixed.

In this way, tertiary reforming means a considerable simplification, taking advantage of the Absence of high temperature pipe walls and the fact that the pipes are under perfectly balanced conditions Pressure in the warmest point and therefore the absence of mechanical stress.

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The ammonia generation is expediently under absolute

th pressures of less than 100 kg / cm, in particular from 40 to 80 kg / cm ² carried out. Thus, the amount of energy required to compress the synthesis mixture is considerably reduced.

Compartment of an advantageous embodiment of the invention The process involves regenerating the molecular sieves through at least part of the from the Ammonia generation flowing out converted gas, through which the adsorbed water and the remaining adsorbed Ammonia are stripped off, and this gas is then passed to ammonia absorption.

In this way, the temperature change of the gas from the outlet of the synthesis reaction ^{device (dry at about 420 0} O) to the outlet of the ammonia absorption device (wet at about 40 ° C) can be used under isobaric conditions to both the gas drying and the regeneration of the adsorbent Masses of molecular sieves can be carried out without the need for any heat input and cooling units from the outside. Furthermore, this allows the reduction of the ammonia content in the gas fed to the synthesis reaction, which is the fresh synthesis mixture produced by the hydrocarbons, to which the ammonia-free gas leaving the ammonia absorption has been added before the drying mentioned, to a minimum, what is of great importance for achieving good conversions, especially in ammonia generating plants operated at low pressure.

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It is advisable to use four molecular sieves for drying the gas to be supplied to the ammonia production. which individually and alternately in each operating cycle operated so that one in the regeneration stage, one in the heating stage, one in the cooling stage and one is operated in the adsorption stage.

Advantageously, the converted gas leaving the ammonia production is converted into a molecular sieve before it is converted into a molecular sieve the regeneration stage with preheating of the dried material coming from the molecular sieve in the adsorption stage Gas cooled.

It is also advantageous to use the reacted gas leaving the molecular sieve in the regeneration stage before it is directed to the ammonia absorption, the dried material flowing out of the molecular sieve in the adsorption stage Preheat gas.

The heating of the molecular sieve in the heating stage by utilizing the molecular sieve is expedient accomplished in the cooling stage withdrawn heat.

It is also advantageous to have some of the dried material coming from the molecular sieve in the adsorption stage To conduct gas to the molecular sieve in the cooling stage and from this to the molecular sieve in the heating stage.

Furthermore, the gas flowing out from the molecular sieve in the heating stage is expediently used for ammonia absorption guided.

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Furthermore, the ammonia absorption is expedient leaving gas after the addition of fresh synthesis mixture and after compression, in particular by means of a circulator, passed to the molecular sieve in the adsorption stage.

According to an advantageous embodiment of the invention Method, the distillation of the ammonia solution is carried out in such a way that the to be distilled Ammonia solution after it has been mixed with that from the top of the lower pressure distillation column flowing ammonia vapors fed to the distillation column operating at higher pressure is, from the bottom of the partially distilled ammonia solution to the lower pressure distillation column is passed and the liquid ammonia at the top of the column operating at higher pressure while the remaining solution is drawn off at the bottom of the lower pressure column

In this way, the distillation can be carried out at low temperatures, for example at temperatures of about 150 to 140 ⁰ G, which allows the recovery heat to be used at a low heat level, which is generally available in large quantities in modern ammonia production plants .

The one flowing out from the upper end of the lower pressure distillation column is advantageous Ammonia vapors mixed ammonia solution to be distilled before being sent to the working at higher pressure Distillation column condenses in particular

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in a downflow film type cooler.

It is also convenient to use those from the top the ammonia vapors flowing out of the lower pressure distillation column mixed to be distilled Ammonia solution before being passed to the higher pressure distillation column through the bottom the remaining solution withdrawn from the lower pressure distillation column is preheated.

According to an advantageous embodiment of the method according to the invention, the at the top of the with Higher pressure working distillation column recovered liquid ammonia to obtain cooled liquid Ammonia is allowed to expand while the vapors evolved from this expansion, if necessary after their condensation, are mixed with the ammonia solution to be distilled.

It is preferred here to allow the liquid ammonia obtained at the upper end of the higher pressure distillation column to expand in two stages, the former at the pressure of the lower. ¹ ^ iCk working distillation column and the latter is adjusted to atmospheric pressure, and to mix the vapors developed in the first stage with the ammonia solution to be distilled and the vapors developed in the second stage with part of the remaining withdrawn from the bottom of the lower pressure distillation column To mix solution, to condense and to mix with the ammonia solution to be distilled.

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Preferably, as the distillation column operating at a lower pressure, one of the film type and as The distillation column operating at a higher pressure has a film type in its lower section and a bottom type applied in their upper section.

The invention will be exemplified by way of the following Explanations in connection with the accompanying drawings .explained in more detail.

Here are:

Figure 1 _t the flow diagram of an embodiment of the method according to the invention

FIG. 2 shows the working diagram of an embodiment of the drying stage for ammonia production guided gas of the method according to the invention and

FIG. 3 shows the flow diagram of an embodiment the stage of distillation of the ammonia solution of the process according to the invention.

In the figure 1, the starting hydrocarbons of natural gas through a line 1 after preheating in a preheater 2 and mixing with steam from a steam line 3 in part through one to the former line connected line 4 is fed to a primary reforming device 5, while the rest (about 40 to 50%) through a line 6, also connected to the former line 1, to a tertiary reforming device 7

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will lead. Through another line 71, air is supplied to a process air compressor 13 and a gas turbine 9 and a further line 72 supplies fuel to the gas turbine 9. By one connected to the gas turbine 9 Line 8 is used by the process air compressor 13 operating gas turbine 9 emitted hot oxygen-rich vapors out. These vapors are the combustion medium of the furnace of the primary reforming device 5 with the Burners 10 for heating gas 11. By one with the Veranrensluftkompressor 13 connected line 12 becomes air after compression in the process air compressor 13 and preheating in a built-in preheater 14 of a secondary reforming device 15 »which the gas mixture leaving the primary reforming device 5 through one of the the latter to the secondary reforming device 15 leading line 16 is fed.

The air supply is expediently dimensioned so that the end gas mixture is that required for the ammonia production Composition has.

The one leaving the secondary reforming device 15 A gas mixture at a high temperature will lead to the tertiary reforming device 7 through a \ ·> η of the former Line 17 -the tertiary reforming device 7 is fed.

The tertiary reforming device 7 is of the mixed type, that is, of the type in which the reformed mixture, which is generated by flowing within the tubes 18 of the tertiary reforming device 7 containing the catalyst is, before the heat exchange, directly with the gas mixture passed through said line 17,

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which provides the heat required for reforming, is mixed.

The gas reaction mixture leaving the tertiary reforming device 7 is through a pipe 19 connected to the former after cooling in a cooler a high-temperature reaction device 21 and from this after further cooling in a further cooler a low temperature reaction device 23 is supplied.

The known conversion between carbon oxide and steam to hydrogen and carbon dioxide takes place in the reaction devices 21, 23.

From the low temperature reaction device 23 is the process gas mixture after cooling in further coolers 24, 25 of an absorption column 26 in which as is known, it is connected to the absorption column 26 by means of a known per se Line 27 supplied suitable solution from the largest part of the carbon dioxide it contains is purified. The from the bottom of the absorption column 26 through a connected line 28 flowing out solution is regenerated in a manner known per se, which is shown in the drawing is not shown.

The process gas mixture or the synthesis gas is then discharged from the upper end of the absorption column 26 fed to a methanation reaction device 29, after passing through a heat exchanger 30 utilizing the heat of the methanation reaction device 29 leaving gas mixture and has been preheated by a further heat exchanger 31.

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The known catalytic methanation conversions take place in the methanation reaction device 29 instead of. These reactions are exothermic and, as is known, lead to the removal of those still in the gas mixture contained carbon dioxide and carbon dioxide by reaction with hydrogen.

The synthesis gas generated in this way is cooled further in a further cooler 32. This gas, which the the fresh synthesis mixture produced from the hydrocarbons represents, is then still fed through the said line 19 to a compressor 33 and in this-

sem is compressed to an absolute pressure below 100 kg / cm. The said line 19 connected to said compressor 33 ends at this. (DLe called line 19 thus connects the tertiary reforming device 7 via the above-mentioned devices built into it with this compressor 33)

The gas thus obtained, to which the one connected from the upper end of the ammonia absorption column 34- duxch Line 46 discharging ammonia-free gas is added, after it has been compressed with the aid of a ciwälzers 35 a molecular sieve 36, which in the Figvv 1 shown operating cycle in the Adsorptionsstvfe is forwarded.

At said molecular sieve 36, the gas is in front of his Passing to ammonia generating reaction device 37 dried. The drying system 38 shown in FIG. 1 also has a molecular sieve 36 additional molecular sieve 39 · With this drying system

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is that a molecular sieve 36 (in the figure 1 operating cycle shown) in the adsorption stage and the other molecular sieve 39 (shown in FIG Operating cycle) in the regeneration stage.

In the operating cycle shown in FIG. 1, the water contained in the gas is the first-mentioned Molecular sieve 36 adsorbed and the gas dried in this way after its preheating in heat exchangers 40, 41 of the Ammonia generating reaction device 37 is supplied.

The reacted gas flowing out from the ammonia generating reaction device is converted into the latter Heat exchanger 41 passed, in which it is suitable for the regeneration of the molecular sieves Temperature cools and, as already mentioned, the dried gas coming from the first-mentioned molecular sieve 36 preheated.

The converted gas leaving the relevant heat exchanger 41 is fed to the second-mentioned molecular sieve 39 * which is in the regeneration stage in the operating cycle shown in FIG.

During this regeneration, the gas causes the water and the remaining ammonia to be stripped off, which had previously been adsorbed as the second-mentioned molecular sieve 39 in the synthesis gas drying stage (Adsorption stage) worked.

The gas leaving the "widely-mentioned molecular sieve 39" becomes, after the gas from the first-mentioned molecular sieve 36

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outflowing dried gas in the first-mentioned heat exchanger 40 had preheated further, in another Suhl he cooled 42 and then still through the said Line 4-7, which is connected to the ammonia absorption column 34 ends, this is forwarded. (The said line 47 thus connects via the lines built into it devices indicated above, the first compressor 33 for the synthesis gas with the ammonia absorption column 34).

The upper end of the operated with an aqueous solution Ammonia absorption column 34 · is used by distillation the ammonia solution as illustrated below, aqueous absorption solution coming from a pump 44 through a line connected to the former fed. From the bottom of the ammonia absorption column operated with an aqueous solution 34 is through a line connected to it 45 ammonia solution withdrawn for routing to the distillation.

As already mentioned above, gas 46 freed from ammonia, which is then fed through line 47 to the fresh synthesis mixture, is from the upper end of the ammonia absorption column 34- flow out calmly.

This drying cycle is or will be all of the water which is present during the ammonia absorption in the ammonia absorption column operated with an aqueous solution 34 causes the saturation of the gas in the line 46 leading away from it, as well as the optionally in the line 47 introduced by the line 47 connected to the first compressor for the synthesis gas

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fresh synthesis mixture contained water in simple and efficiently recycled to ammonia absorption · Any remaining ammonia adsorbed is also returned to ammonia absorption during the gas drying stage.

The one obtained at the bottom of the ammonia absorption column 34 and through the line 45 connected to it, ammonia solution is fed by a further pump passed to another cooler 49, from which a Partly through a line 50 branched off from a line 51 connected to this cooler 49 to the ammonia absorption column 34 returned and a part passed through the first-mentioned line 51 for distillation will·

The distillation is carried out in two distillation columns 52, 53 operating at different pressures.

The ammonia solution which is distilled through the line 51 connected to the ammonia absorption column y \ - is allowed to expand after its mixing with the ammonia vapors flowing out from the upper end of the distillation column 52, which operates at a lower pressure than the other distillation column 52, through a line 7 ^ connected to it another cooler 54, preferably of the downflow film type, in which the vapors are condensed. The ammonia solution obtained, which is more concentrated in ammonia than the starting solution, is removed by a further pump after it has been preheated in a heat exchanger 56 built into the line after this at the expense of the bottom

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the remaining solution withdrawn from the distillation column 53 operating at lower pressure and with the higher
Pressure working distillation column 52 supplied.

The highest distillation pressure (higher pressure) depends > on the temperature of the available cooling water and
is on average to about 1? up to 18 kg / cm abs
set.

The minimum distillation pressure (lower pressure) depends. the heat level of the available heat, the final concentration of the ammonia solution to be obtained and! also depends on the temperature of the cooling water. The average pressure is about 5 kg / cm abs. as the optimum
although this value will vary from case to case
can.

In the distillation,

column 52, which is preferably from the downward flowing i

Film type in their lower section and the bottom type in j

its upper section is the one supplied to it} Ammonia solution partially up to one with the operating

dn -. 'V: and with the maximum temperature to be reached in the \

Consistent ammonia concentration, for example! 26% by weight ammonia at 130 ° C. and 18 kg / cm ² abs., Distilled.

Tom Boden of the higher pressure distillation j

column 52 is the partially distilled ammonia solution j

through a line 73 connected to it, which is marked with j

lower pressure distillation column 53 J

supplied, in which their ammonia concentration on the ']

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desired value, for example 10 wt .-%, reduced will. ·

The ammonia vapors rising in the lower section of the higher pressure distillation column 52 are rectified in its upper section of the soil type and connected to it by a Line 75 is fed to a reflux condenser 57, which is built into this line 75, and in this condenses, whereby 99 »9 wt .-% - liquid ammonia is obtained, which is discharged through said line 75 into a container 58.

The lower pressure distillation column 53 is also preferably of the downflow film type.

The one coming from the bottom of the lower pressure distillation column 53 through the one attached to it Line 43 guided residual aqueous absorption solution is after the heat release in the relevant Heat exchanger 56 and a final cooling in another cooler 59 the upper part of the ammonia absorption column 3 ^ back for ammonia absorption forwarded.

The ammonia vapors released in the lower pressure distillation column 53 are as already mentioned by the to the former connected line 7 ^ the through to the ammonia absorption column 34 connected line 51 flowing admixed to distilled ammonia solution.

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Due to the cycle described above, the ammonia solution can with delivery of heat at a low Heat level, for example at temperatures of about 130 to 140 ° C, can be distilled · The use of Film-type distillation devices not only allow the heat and material exchange to occur only on one surface, but also the delivery of heat in countercurrent at average levels below the highest distillation temperature, which is very important.

The reference numerals 64, 65 indicate the amounts of heat at a low heat level which are fed to the distillation columns 52 and 53, respectively.

Part of the ammonia-freed gas coming from the upper end of the ammonia absorption column 34 and flowing through the line 46 connected to it is discharged through a line 60 branched off from the latter line 46 and fed to a hydrogen recovery unit 61 which comprises a cryogenic fractionation unit.

Recovered hydrogen is used by one of the Resin recovery unit 61 leading away line of the fresh synthesis mixture in the relevant Line 19 fed, while the remaining fraction through another from the hydrogen recovery unit 61 away line 63 is fed to the recycling as fuel or heating gas.

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In a plant of the type shown in Figure 1 was with an available natural gas under one Pressure of 45 kg / cm abs. when carrying out the production of the synthesis gas under a pressure of about 40 kg / cm abs. and ammonia production under a pressure of 60 kg / cm abs. at one generation of non-cooled 99.9% liquid ammonia achieves an efficiency of about 6596.

FIG. 2 shows a modified embodiment of the drying system shown in FIG In this system, the drying of the gas is ceased before it is sent to the ammonia generating reaction device Use of four molecular sieves, one of which is used individually and alternately in each operating cycle Regeneration stage, one in the heating stage, one in the cooling stage and one in the adsorption stage is carried out. The molecular sieve in the heating stage is replaced by the molecular sieve in the cooling stage removed heat is heated.

In Figure 2, there are four molecular sieves 101, 102, 103, 104. That is the ammonia generating reaction device The reacted gas leaving 105 is passed through a line 118 connected to it through a heat exchanger "106, in which it is on a temperature suitable for the regeneration of the molecular sieves 101, 102, 103, 104 simultaneous preheating of the operating cycle shown in FIG. 2 in the adsorption stage Molecular sieve 104 through a

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leading line 115 outflowing dried gas is cooled, performed. The dried gas preheated in this way is passed through the said heat exchanger The latter line 115 passed to the ammonia generating reaction device 105.

The converted gas leaving said heat exchanger 106 is fed through the relevant line 118 to the molecular sieve 101 located in the regeneration stage in the operating cycle shown in FIG. The gas flowing out of this molecular sieve 101 is through a line 119 leading away from the latter molecular sieve 101 after its cooling with further preheating of the molecular sieve 104 located in the adsorption stage in the operating cycle shown in FIG further heat exchanger 107 in a still further heat exchanger 108 cooled further ^ ¹¹ ^ then fed to the absorption of ammonia with water in an ammonia absorption column 109.

The necessary for absorbing water is supplied by a ^v connected to the top of the ammonia absorption column line 110 to the top of the ammonia absorption column 109th From the bottom of the latter, ammonia solution is drawn off through a line connected to it and sent to the distillation.

The gas, which has been freed of ammonia and saturated with water, is

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Sorption column 109 connected line 112 from left the upper end of the ammonia absorption column 109 to flow out. This gas is replaced by the latter Line 112 after it has been compressed by means of a circulator 11 built into the middle. to the Molecular sieve 104 located in the adsorption stage in the operating cycle shown in FIG.

The fresh synthesis mixture coming from the unit for generating the synthesis gas from hydrocarbons for ammonia production is through a respective line 114 through the to the upper end the line 112 connected to the ammonia absorption column 109 is supplied with ammonia-freed gas, before it goes through this line 112 to the operating cycle shown in FIG Adsorption stage located molecular sieve 104 is supplied. In this latter molecular sieve 104 the water contained in the gas is completely adsorbed,

The largest part of the gas dried in this way, namely about 95 wt .- #, is by the from the in the figure 2 Line 115 leading away the molecular sieve 104 located in the adsorption stage in the operating cycle shown after being preheated in the respective heat exchangers 107, 106 of the ammonia generating reaction device 105 forwarded. Part of the dried molecular sieve 104 coming from the operating cycle shown in FIG. 2 in the adsorption stage Gas, namely about 5 wt .-%, on the other hand, is discharged from the last-mentioned line 115

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branched line 116 to the molecular sieve located in the cooling stage in the operating cycle shown in FIG 103 and of this the one in the heating stage in the operating cycle shown in FIG Molecular sieve 102 supplied. The gas passed through the latter line 116 leads from the hot mass of the operating cycle shown in FIG. 2 in the cooling stage and in the previous operating cycle in the regeneration stage which has been molecular sieve 103 heat and transfers this heat to the cold mass of the operating cycle shown in FIG. 2 in the cooling stage Molecular sieve 102, which has to come into the regeneration stage in the next operating cycle, as set out in more detail below.

The molecular sieve located in the heating stage in the operating cycle shown in FIG 102 outflowing gas is through a line 117 leading away from the latter molecular sieve 102 to the im In the operating cycle shown in Figure 2 in the regeneration stage through molecular sieve 101 The gate leaving the latter "leading away line 119" is admixed and, together with this, the ammonia absorption column 109 supplied.

In this way, all of the water that is in the Ammonia absorption column 109 for saturation of this leads through the line of leaving gas connected to its upper end, as well as possibly in

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the fresh synthesis mixture supplied through the relevant line 114 simply contains water and effectively recycled to ammonia absorption. Even that during the drying stage of the conduit 112 connected to the upper end of the ammonia absorption column 109, if appropriate Any adsorbed residual ammonia is returned to the ammonia absorptlon.

As has already been explained, both the operating cycle shown in FIG The gas flowing out of the molecular sieve located in the regeneration stage as well as the gas flowing out from the in FIG operating cycle shown in the heating stage in the molecular sieve 102 flowing out gas to Ammonia absorption column 109 passed.

After a predetermined period of time, the molecular sieve operating cycle described above begins 101, 102, 103, 104 converted so that the operating cycle shown in Figure 2 in the Molecular sieve 102 located in the heating stage Regeneration stage comes while the im in the Figure 2 operating cycle located in the regeneration stage, cooling stage or adsorption stage Molecular sieves 101, 103, 104 come into the cooling stage, adsorption stage or heating stage.

Such a changeover can be achieved by means known per se, which is shown in FIG Is not shown for the sake of simplicity. She will then

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made when the temperature of the operating cycle shown in Figure 2 in the heating stage located molecular sieve 102 of the temperature of the operating cycle shown in Figure 2 in the Molecular sieve 101 located in the regeneration stage approximates and the temperature of the molecular sieve shown in FIG Operating cycle in the cooling stage located molecular sieve 103 in the vicinity of the temperature of the im The operating cycle of the molecular sieve 104 in the adsorption stage shown in FIG comes.

The change in the operating cycle can be carried out in a simple manner without creating thermal imbalances be performed. Also, such a change does not lead to pressure imbalances, since the operating cycle is of the isobaric type in which the im in the Figure 2 operating cycle shown in the adsorption molecular sieve 104 located on the delivery side of the circulator 113 concerned, while the other 3 molecular sieves 101, 102, 103 through the at the outlet of the Ammonia generating device 105 prevailing pressure can be adjusted. This makes one possible in itself Ve. contamination of the dried gas by the wet gas is impossible.

The frequency of changing the operating cycle of the molecular sieves 101, 102, 103, 104 is generally very high, for example hourly, so that a drastic reduction in the dimensions of the molecular sieves 101, 102, 103, 104 itself is achieved.

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Nevertheless, the duration of the operating cycle and the regeneration temperature of the molecular sieves 101, 102, 103, 104 as a function of the type of adsorption mass of the molecular sieves 101, 102, 103, 104 chosen.

With reference to the accompanying Figure 2 are the possible consequences of the operating cycles of the molecular sieves 101, 102, 103, 104 four, as illustrated in the table below.

Tabel

Level of be
to say the least
of A. Molecule
Operating
B. irsieve ii
•Cycle
C. η
D. adsorption 104 103 101 102 Cooling 103 101 102 104 Warming 102 _ 104 103 101 regeneration 101 102 104 103

From the table above it can be seen that operating cycle A, which is the one shown in FIG

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and in which the molecular sieve 101 is in the regeneration stage, the molecular sieve 104 is in the adsorption stage and molecular sieves 103 and 102 are in the cooling stage, respectively Heating stage are followed by operating cycle B, then operating cycle C and finally operating cycle D, "which in turn precedes operating cycle A, the operating cycles repeat in this way. Thus, of the four molecular sieves 101, 102, 103, 104 are single and alternately in feathers operating cycle one in the Regeneration stage, one in the heating stage, one in the cooling stage and one in the adsorption stage.

In many cases it is also necessary for storage requirements refrigerated to -33 ° C and below To generate liquid ammonia located at atmospheric pressure. In such cases, the one in FIG. 1 The distillation cycle shown is modified from that shown in FIG. 3, wherein in the FIG. 3, the same parts are denoted by the same reference numerals as in FIG. 1.

In FIG. 3, at the upper end of the distillation column 52, which operates at a higher pressure, is obtained liquid ammonia discharged through a line 76 connected to it and in two stages in containers 68, 69 allowed to expand, the first container 68 with the pressure of the lower Pressure operated distillation column 53 and the

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second container 69 is matched to the atmospheric pressure

The vapors developed in the first container 68 are through a connected to it line 77 and the one at the upper end of the lower pressure working distillation column 53 connected line 74, into which the former opens, with the through the one connected to the ammonia absorption column 34 Line 51 out to be distilled ammonia solution mixed and then in this Condenser 54 installed in line 51 condenses, while those in the second container 69 developed Vapors by conducting them through a line 78 connected to it with part of the from Bottom of the lower pressure distillation column 53 coming through the one connected to it Line 43 conducted remaining aqueous absorption solution, which part by one of the latter Line 43 branched line 79, into which the first-mentioned line 78 opens, is passed, mixed and then condensed in a respective cooler 66, from the latter of which they are condensed by means of an associated Pump 67 also of the line connected to the ammonia absorption column 34 guided ammonia solution to be distilled are admixed.

The cooled liquid ammonia is in a container 70, in which the at the higher pressure working distillation column 52 connected line 76 opens, won.

Abstract 130049/0517

Claims (16)

Claims 1.) Process for the production of ammonia by generating synthesis gas from hydrocarbons their primary reforming with steam and secondary reforming of the gas mixture obtained with oxygen and downstream production of ammonia, characterized in that part of the with the Steam mixed starting hydrocarbons undergo a tertiary reforming process, which is given the necessary heat through which the secondary reforming leaving reaction gas mixture supplies, subjects the Ammonia production under low pressure with drying of the gas fed to it by using Molecular sieves carried out, the ammonia contained in the converted gas can be absorbed by water and the ammonia solution thus obtained is distilled using two distillation columns operating at different pressures. 2.) The method according to claim 1, characterized in that one of the mixed type as tertiary reforming applies. 3.) Process according to claim 1 or 2, characterized in that the ammonia production is carried out under absolute pressures of less than 100 kg / cm, in particular of 40 to 80 kg / cm. 4.) Process according to claim 1 to 3, characterized in that the regeneration of the molecular sieves is carried out by - 3 -130049/0517 at least part of the reacted gas flowing out of the ammonia generation carries out and this Gas then passes to ammonia absorption. 5.) The method according to claim 1 to 4, characterized in that for drying the ammonia to be supplied to Gas used four molecular sieves, which one individually and alternately in each operating cycle operates that one in the regeneration stage, one in the heating stage, one in the cooling stage and lets one operate in the adsorption stage. 6 ·) Process according to claims 1 to 5 »characterized in that the converted gas leaving the ammonia production is converted into the hegeneration stage with preheating of the dried material coming from the molecular sieve in the adsorption stage Gas cools. 7.) Process according to claim 1 to 6, characterized in that with the reacted gas leaving the molecular sieve in the regeneration stage before it is passed to ammonia absorption, the dried q _{& b flowing out of the molecular sieve in the adsorption stage before} «. warmed up. 8.) The method according to claim 1 to 7 »characterized in that the heating of the molecular sieve in the Heating stage through utilization of the molecular sieve accomplished in the cooling stage withdrawn heat. 130043/0517 9.) Method according to claim 1 to 8, characterized in that that one part of the coming from the molecular sieve in the adsorption dried gas to Molecular sieve in the cooling stage and from this to the molecular sieve in the heating stage. 10.) The method according to claim 1 to 9 »characterized in j that you get that from the molecular sieve in the heating stage escaping gas leads to ammonia absorption. 11.) The method according to claim 1 to 10, characterized in that that the gas leaving the ammonia absorption after the addition of fresh synthesis mixture and after compression to the molecular sieve in the adsorption stage. 12.) The method according to claim 1 to 11, characterized in that that one carries out the distillation of the ammonia solution in such a way that the ammonia solution to be distilled is carried out after mixing them with those from the top of the lower pressure distillation column ammonia vapors flowing out of the distillation column operating at a higher pressure, from tsren soil the partially distilled ammonia solution to the lower pressure distillation column and the liquid ammonia at the top of the column operating at higher pressure wins, while the remaining solution is on Draws off the bottom of the lower pressure column. - 5 -130049/0517 13.) The method of claim 1 to 12, characterized in that with the effluent from the upper end of the working lower pressure distillation column ammonia vapors mixed to be distilled ammonia "solution prior to its passing to the working at higher pressure distillation column condensed. 14.) Method according to claim 1 to 12, characterized in that that one with the from the upper end of the lower pressure operating distillation column flowing out Ammonia vapors mixed ammonia solution to be distilled before being sent to the working at higher pressure Distillation column through that from the bottom of the lower pressure distillation column preheated residual solution withdrawn. 15 ·) Method according to claim 1 to 14, characterized in that one at the upper end of the with higher Pressure working distillation column recovered liquid ammonia while obtaining cooled liquid ammonia can be expanded, while the vapors developed by this expansion, optionally after their condensation, mixed with the ammonia solution to be distilled. 16.) The method according to claim 1 to 15, characterized in that the at the upper end of the with higher Liquid ammonia obtained from a pressure distillation column can be expanded in two stages, the former with the pressure of the lower pressure distillation column and the latter co-ordinates with atmospheric pressure, and the vapors evolved in the first stage with - 6 130049/0517 mixed with the ammonia solution to be distilled and the vapors developed in the second stage with it part of the remainder withdrawn from the bottom of the lower pressure distillation column Solution mixed, condensed and mixed with the ammonia solution to be distilled 17 ·) Process according to claim 1 to 16, characterized in that one is working with lower pressure The distillation column is of the film type and operates at a higher pressure The distillation column has a film type in its lower section and a tray type in its above section applies. description 130049/0517