Title of Invention	A PROCESS AND A REACTOR FOR THE PREPARATION OF AMMONIA
Abstract	The invention relates to a process for the preparation of ammonia at elevated pressure and temperature in an ammonia reactor, comprising passing a process stream of ammonia synthesis gas successively through at least three catalyst beds and reacting the synthesis gas in the beds; intermediately cooling of partially reacted synthesis gas leaving the catalyst beds by heat exchange in heat exchangers arranged between each catalyst bed and withdrawing a product effluent being rich in ammonia, wherein the process stream is obtained by combining prior to introduction into a first catalyst bed, a first feed stream of synthesis gas having been preheated through indirect heat exchange during the intermediate cooling of the partially converted synthesis gas, a second feed stream of synthesis gas having been preheated by indirect heat exchange with the product effluent, and a third feed stream of synthesis gas for adjustment of temperature of the process stream and wherein the first feed stream is passed successively through the interbed heat exchangers for cooling the partially converted synthesis gas. The invention also relates to a reactor for the preparation of ammOnIa.

Title of Invention

A PROCESS AND A REACTOR FOR THE PREPARATION OF AMMONIA

Abstract

The invention relates to a process for the preparation of ammonia at elevated pressure and temperature in an ammonia reactor, comprising passing a process stream of ammonia synthesis gas successively through at least three catalyst beds and reacting the synthesis gas in the beds; intermediately cooling of partially reacted synthesis gas leaving the catalyst beds by heat exchange in heat exchangers arranged between each catalyst bed and withdrawing a product effluent being rich in ammonia, wherein the process stream is obtained by combining prior to introduction into a first catalyst bed, a first feed stream of synthesis gas having been preheated through indirect heat exchange during the intermediate cooling of the partially converted synthesis gas, a second feed stream of synthesis gas having been preheated by indirect heat exchange with the product effluent, and a third feed stream of synthesis gas for adjustment of temperature of the process stream and wherein the first feed stream is passed successively through the interbed heat exchangers for cooling the partially converted synthesis gas. The invention also relates to a reactor for the preparation of ammOnIa.

Full Text	The present invention relates to a process and reactor for the preparation of ammonia from a synthesis gas comprising nitrogen and hydrogen by passage of the syn¬thesis gas through a number of catalyst beds with inter¬mediate cooling of partially converted synthesis gas between the catalyst beds. In particular, the invention concerns an improved process of the above type and an ammonia reactor for use in the process, wherein cooling of the partially converted synthesis gas is performed by indirect heat exchange with a single stream of fresh syn¬thesis gas. US Patent No. 4,181,701 discloses an ammonia reac¬tor with a top and a bottom catalyst bed with a central heat exchanger mounted on one of the beds, "A process stream of synthesis gas is obtained by combining inside the reac¬tor separate feed streams; a shell stream serving to cool the reactor shell, an exchange stream serving to cool the central heat exchanger, and a by-pass stream for final adjustment of the temperature of the process stream. Indirect cooling of partially converted ammonia synthesis gas in a reactor with more than two catalyst beds is, furthermore, known in the art and conventionally applied for in the industry. Thereby, the synthesis gas is indirectly cooled with fresh synthesis gas being passed in a number of separ¬ate streams to heat exchangers between the catalyst beds. The streams are introduced through separate pipe connec¬tions mounted in the reactor shell. The major drawback of the known ammonia preparation processes with intermediate cooling of partially converted synthesis gas in a number of interbed heat exchangers with separate gas streams is the need for numerous inlet means and complicated piping in the ammonia reactor. It is thus an object of this invention to provide a process for the preparation of ammonia in more than two catalyst beds with intermediate cooling of partially converted synthesis gas, wherein the gas is cooled between the catalyst beds by indirect heat exchange without the above drawbacks of the known processes. Accordingly, the present invention provides a process for the preparation of ammonia at elevated pressure and temperature in an ammonia reactor, comprising passing a process stream of ammonia synthesis gas successively through at least three catalyst beds and reacting the synthesis gas in the beds; intermediately cooling of partially reacted synthesis gas leaving the catalyst beds by heat exchange in heat exchangers arranged between each catalyst bed and withdrawing a product effluent being rich in ammonia, wherein the process stream is obtained by combining prior to introduction into a first catalyst bed, a first feed stream of synthesis gas having been preheated through indirect heat exchange during the intermediate cooling of the partially converted synthesis gas, a second feed stream of synthesis gas having been preheated by indirect heat exchange with the product effluent, and a third feed stream of synthesis gas for adjustment of temperature of the process stream and wherein the first feed stream is passed successively through the interbed heat exchangers for cooling the partially converted synthesis gas. A further object of the invention is to provide an ammonia reactor for use in the inventive process with simplified inlet and piping means for distribution of fresh synthesis gas serving as cooling medium in indirect heat exchange with partially reacted synthesis gas between each catalyst bed. Accordingly, the present invention also provides a reactor for the preparation of ammonia comprising within a cylindrical pressure shell at least a first, a second and a last catalyst bed vertically arranged around a common axis and connected in series; intermediate heat exchangers arranged between each catalyst bed for intermediate cooling of a partially converted ammonia synthesis gas from the catalyst bed by indirect heat exchange with a first feed stream of fresh ammonia synthesis gas; feed-effluent heat exchanger arranged at outlet of the last catalyst bed for cooling of an ammonia product effluent stream by indirect heat exchange with a second feed stream of ammonia synthesis gas; inlet means for introducing the first feed stream of fresh synthesis gas into the reactor; inlet means for introducing the second feed stream of fresh synthesis gas into the reactor; inlet means for introducing a third feed stream of fresh ammonia synthesis gas into the reactor; passage-ways for passing the first, the second and the third feed stream to the top catalyst bed; and passage-ways for combining the feed streams to a process stream prior to introduction of the process stream into the top catalyst bed, wherein the passage-ways for passing the first feed stream consists of a passage-way for passing the first feed stream through the intermediate heat exchangers in series and for passing the first feed stream fi"om the inlet means consecutively through the intermediate heat exchangers to the passage¬ways for combining the first, the second and the third feed stream. The invention will be explained in more detail in the following description by reference to the drawings, in which the sole Figure shows in pure schematic form a sectional view of an ammonia reactor according to a specific embodiment of the invention. When operating the invention, fresh ammonia syn¬thesis gas 2 is introduced into an ammonia reactor 4 being constructed according to a specific embodiment of the invention. The synthesis gas is introduced in three separ¬ate feed streams 6, 8, 10 through inlets 16, 18 and 2 0 arranged in shell 12 of the reactor. Reactor 4 comprises within the shell a top catalyst bed 24, a central catalyst bed 26 and a bottom catalyst bed 28. Between beds 24 and 26 and between beds 26 and 28 heat exchangers 3 0 and 32 are arranged for cooling a partly converted process stream 37 leaving beds 24 and 26. A bottom heat exchanger 34 arranged downstream bottom catalyst bed 28 serves for cooling of a product effluent 38 from bed 28. Fresh synthesis gas is passed in process stream 3 6 to bed 24 and partly converted in bed 24. The partly converted synthesis gas is then passed in process stream 37 successively through beds 26 and 28. By passage through the beds nitrogen and hydrogen in the stream react exothermically to ammonia and product effluent 38 being rich in ammonia. Product effluent 38 is cooled in heat exchanger 34 by indirect cooling with feed stream 8 before being withdrawn from the reactor through outlet 40. As mentioned hereinbefore, the reaction between hydrogen and nitrogen proceeds exothermically in the cata¬lyst beds and the temperature of the process stream rises. Because of thermodynamical reasons the temperature of process stream 37 has to be lowered, prior to being intro¬duced into beds 26 and 28. The stream is thereby cooled in heat exchangers 3 0 and 32 by indirect heat exchange with feed stream 6, being passed in series through heat exchangers 3 2 and 30. By passage through the heat exchangers feed streams 6 and 8 are preheated by indirect heat exchange as described above. The preheated feedstreams are then com¬bined to process stream 3 6 upstream top catalyst bed 24. Before being introduced in bed 24, the temperature of process stream 36 is adjusted by addition of a cold feed stream 10. WE CLAIM; 1. A process for the preparation of ammonia at elevated pressure and temperature in an ammonia reactor, comprising passing a process stream of ammonia synthesis gas successively through at least three catalyst beds and reacting the synthesis gas in the beds; intermediately cooling of partially reacted synthesis gas leaving the catalyst beds by heat exchange in heat exchangers arranged between each catalyst bed and withdrawing a product effluent being rich in ammonia, wherein the process stream is obtained by combining prior to introduction into a first catalyst bed, a first feed stream of synthesis gas having been preheated through indirect heat exchange during the intermediate cooling of the partially converted synthesis gas, a second feed stream of synthesis gas having been preheated by indirect heat exchange with the product effluent, and a third feed stream of synthesis gas for adjustment of temperature of the process stream and wherein the first feed stream is passed successively through the interbed heat exchangers for cooling the partially converted synthesis gas. 2. A reactor for the preparation of ammonia comprising within a cylindrical pressure shell (12) at least a first (24), a second (26) and a last (28) catalyst bed vertically arranged around a common axis and connected in series; intermediate heat exchangers (30), (32) arranged between each catalyst bed for intermediate cooling of a partially converted ammonia synthesis gas (37) from the catalyst bed by indirect heat exchange with a first feed stream (6) of fresh ammonia synthesis gas; feed-effluent heat exchanger (34) arranged at outlet of the last catalyst bed (28) for cooling of an ammonia product effluent stream (38) by indirect heat exchange with a second feed stream (8) of ammonia synthesis gas; inlet means (16) for introducing the first feed stream (6) of fresh synthesis gas into the reactor (4); inlet means (18) for introducing the second feed stream (8) of fresh synthesis gas into the reactor (4); inlet means (20) for introducing a third feed stream (10) of fresh ammonia synthesis gas into the reactor (4); passage-ways for passing the first (6), the second (8) and the third (10) feed stream to the top catalyst bed (24); and passage-ways for combining the feed streams to a process stream (36) prior to introduction of the process stream (36) into the top catalyst bed (24), wherein the passage-ways for passing the first feed stream (6) consists of a passage-way for passing the first feed stream (6) through the intermediate heat exchangers (32), (30) in series and for passing the first feed stream (6) from the inlet means (16) consecutively through the intermediate heat exchangers (32), (30) to the passage-ways for combining the first (6), the second (8) and the third (10) feed stream. 3. A process for the preparation of ammonia substantially as herein described with reference to the accompanying drawing. 4. A reactor for the preparation of ammonia substantially as herein described with reference to the accompanying drawing.

Full Text

The present invention relates to a process and reactor for the preparation of ammonia from a synthesis gas comprising nitrogen and hydrogen by passage of the syn¬thesis gas through a number of catalyst beds with inter¬mediate cooling of partially converted synthesis gas between the catalyst beds. In particular, the invention concerns an improved process of the above type and an ammonia reactor for use in the process, wherein cooling of the partially converted synthesis gas is performed by indirect heat exchange with a single stream of fresh syn¬thesis gas.
US Patent No. 4,181,701 discloses an ammonia reac¬tor with a top and a bottom catalyst bed with a central heat exchanger mounted on one of the beds, "A process stream of synthesis gas is obtained by combining inside the reac¬tor separate feed streams;
a shell stream serving to cool the reactor shell, an exchange stream serving to cool the central heat exchanger, and a by-pass stream for final adjustment of the temperature of the process stream.
Indirect cooling of partially converted ammonia synthesis gas in a reactor with more than two catalyst beds is, furthermore, known in the art and conventionally applied for in the industry.
Thereby, the synthesis gas is indirectly cooled with fresh synthesis gas being passed in a number of separ¬ate streams to heat exchangers between the catalyst beds. The streams are introduced through separate pipe connec¬tions mounted in the reactor shell.
The major drawback of the known ammonia preparation processes with intermediate cooling of partially converted synthesis gas in a number of interbed heat exchangers with separate gas streams is the need for numerous inlet means and complicated piping in the ammonia reactor.

It is thus an object of this invention to provide a process for the preparation of ammonia in more than two catalyst beds with intermediate cooling of partially converted synthesis gas, wherein the gas is cooled between the catalyst beds by indirect heat exchange without the above drawbacks of the known processes.
Accordingly, the present invention provides a process for the preparation of ammonia at elevated pressure and temperature in an ammonia reactor, comprising passing a process stream of ammonia synthesis gas successively through at least three catalyst beds and reacting the synthesis gas in the beds; intermediately cooling of partially reacted synthesis gas leaving the catalyst beds by heat exchange in heat exchangers arranged between each catalyst bed and withdrawing a product effluent being rich in ammonia, wherein the process stream is obtained by combining prior to introduction into a first catalyst bed, a first feed stream of synthesis gas having been preheated through indirect heat exchange during the intermediate cooling of the partially converted synthesis gas, a second feed stream of synthesis gas having been preheated by indirect heat exchange with the product effluent, and a third feed stream of synthesis gas for adjustment of temperature of the process stream and wherein the first feed stream is passed successively through the interbed heat exchangers for cooling the partially converted synthesis gas.
A further object of the invention is to provide an ammonia reactor for use in the inventive process with simplified inlet and piping means for distribution of fresh synthesis gas serving as cooling medium in indirect heat exchange with partially reacted synthesis gas between each catalyst bed.

Accordingly, the present invention also provides a reactor for the preparation of ammonia comprising within a cylindrical pressure shell at least a first, a second and a last catalyst bed vertically arranged around a common axis and connected in series; intermediate heat exchangers arranged between each catalyst bed for intermediate cooling of a partially converted ammonia synthesis gas from the catalyst bed by indirect heat exchange with a first feed stream of fresh ammonia synthesis gas; feed-effluent heat exchanger arranged at outlet of the last catalyst bed for cooling of an ammonia product effluent stream by indirect heat exchange with a second feed stream of ammonia synthesis gas; inlet means for introducing the first feed stream of fresh synthesis gas into the reactor; inlet means for introducing the second feed stream of fresh synthesis gas into the reactor; inlet means for introducing a third feed stream of fresh ammonia synthesis gas into the reactor; passage-ways for passing the first, the second and the third feed stream to the top catalyst bed; and passage-ways for combining the feed streams to a process stream prior to introduction of the process stream into the top catalyst bed, wherein the passage-ways for passing the first feed stream consists of a passage-way for passing the first feed stream through the intermediate heat exchangers in series and for passing the first feed stream fi"om the inlet means consecutively through the intermediate heat exchangers to the passage¬ways for combining the first, the second and the third feed stream.
The invention will be explained in more detail in the following description by reference to the drawings, in which the sole Figure shows in pure schematic form a sectional view of an ammonia reactor according to a specific embodiment of the invention.

When operating the invention, fresh ammonia syn¬thesis gas 2 is introduced into an ammonia reactor 4 being constructed according to a specific embodiment of the invention. The synthesis gas is introduced in three separ¬ate feed streams 6, 8, 10 through inlets 16, 18 and 2 0 arranged in shell 12 of the reactor. Reactor 4 comprises within the shell a top catalyst bed 24, a central catalyst bed 26 and a bottom catalyst bed 28. Between beds 24 and 26 and between beds 26 and 28 heat exchangers 3 0 and 32 are arranged for cooling a partly converted process stream 37 leaving beds 24 and 26. A bottom heat exchanger 34 arranged downstream bottom catalyst bed 28 serves for cooling of a product effluent 38 from bed 28. Fresh synthesis gas is passed in process stream 3 6 to bed 24 and partly converted in bed 24. The partly converted synthesis gas is then passed in process stream 37 successively through beds 26 and 28. By passage through the beds nitrogen and hydrogen in the stream react exothermically to ammonia and product effluent 38 being rich in ammonia. Product effluent 38 is cooled in heat exchanger 34 by indirect cooling with feed stream 8 before being withdrawn from the reactor through outlet 40.
As mentioned hereinbefore, the reaction between hydrogen and nitrogen proceeds exothermically in the cata¬lyst beds and the temperature of the process stream rises. Because of thermodynamical reasons the temperature of process stream 37 has to be lowered, prior to being intro¬duced into beds 26 and 28. The stream is thereby cooled in heat exchangers 3 0 and 32 by indirect heat exchange with feed stream 6, being passed in series through heat exchangers 3 2 and 30.

By passage through the heat exchangers feed streams 6 and 8 are preheated by indirect heat exchange as described above. The preheated feedstreams are then com¬bined to process stream 3 6 upstream top catalyst bed 24. Before being introduced in bed 24, the temperature of process stream 36 is adjusted by addition of a cold feed stream 10.

WE CLAIM;
1. A process for the preparation of ammonia at elevated pressure and temperature in an ammonia reactor, comprising passing a process stream of ammonia synthesis gas successively through at least three catalyst beds and reacting the synthesis gas in the beds; intermediately cooling of partially reacted synthesis gas leaving the catalyst beds by heat exchange in heat exchangers arranged between each catalyst bed and withdrawing a product effluent being rich in ammonia, wherein the process stream is obtained by combining prior to introduction into a first catalyst bed, a first feed stream of synthesis gas having been preheated through indirect heat exchange during the intermediate cooling of the partially converted synthesis gas, a second feed stream of synthesis gas having been preheated by indirect heat exchange with the product effluent, and a third feed stream of synthesis gas for adjustment of temperature of the process stream and wherein the first feed stream is passed successively through the interbed heat exchangers for cooling the partially converted synthesis gas.
2. A reactor for the preparation of ammonia comprising within a cylindrical pressure shell (12) at least a first (24), a second (26) and a last (28) catalyst bed vertically arranged around a common axis and connected in series; intermediate heat exchangers (30), (32) arranged between each catalyst bed for intermediate cooling of a partially converted ammonia synthesis gas (37) from the catalyst bed by indirect heat exchange with a first feed stream (6) of fresh ammonia synthesis gas; feed-effluent heat exchanger (34) arranged at outlet of the last catalyst bed (28) for cooling of an ammonia product effluent stream (38) by indirect heat exchange with a second feed stream (8) of ammonia synthesis

gas; inlet means (16) for introducing the first feed stream (6) of fresh synthesis gas into the reactor (4); inlet means (18) for introducing the second feed stream (8) of fresh synthesis gas into the reactor (4); inlet means (20) for introducing a third feed stream (10) of fresh ammonia synthesis gas into the reactor (4); passage-ways for passing the first (6), the second (8) and the third (10) feed stream to the top catalyst bed (24); and passage-ways for combining the feed streams to a process stream (36) prior to introduction of the process stream (36) into the top catalyst bed (24), wherein the passage-ways for passing the first feed stream (6) consists of a passage-way for passing the first feed stream (6) through the intermediate heat exchangers (32), (30) in series and for passing the first feed stream (6) from the inlet means (16) consecutively through the intermediate heat exchangers (32), (30) to the passage-ways for combining the first (6), the second (8) and the third (10) feed stream.
3. A process for the preparation of ammonia substantially as herein described
with reference to the accompanying drawing.
4. A reactor for the preparation of ammonia substantially as herein described with
reference to the accompanying drawing.

Documents:

828-mas-1998 abstract duplicate.pdf

828-mas-1998 abstract.pdf

828-mas-1998 claims duplicate.pdf

828-mas-1998 claims.pdf

828-mas-1998 correspondence others.pdf

828-mas-1998 correspondence po.pdf

828-mas-1998 description (complete) duplicate.pdf

828-mas-1998 description (complete).pdf

828-mas-1998 drawing.pdf

828-mas-1998 form-19.pdf

828-mas-1998 form-2.pdf

828-mas-1998 form-26.pdf

828-mas-1998 form-4.pdf

828-mas-1998 form-6.pdf

828-mas-1998 others.pdf

828-mas-1998 petition.pdf

« Previous Patent

Next Patent »

Patent Number

200973

Indian Patent Application Number

828/MAS/1998

PG Journal Number

8/2007

Publication Date

23-Feb-2007

Grant Date

19-Jun-2006

Date of Filing

20-Apr-1998

Name of Patentee

M/S. HALDOR TOPSOE A/S

Applicant Address

NYMOLLEVEJ 55, DK-2800 LYUGBY,

Inventors:

#	Inventor's Name	Inventor's Address
1	ERIK ANDREAS GAM	MOLLEVEJ 22, DK-2970 HORSHOLM,

PCT International Classification Number

C01C 01/04

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	0444/97	1997-04-21	Denmark