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WO2018184731A1 - Process and plant for minimizing the emissions of nitrogen oxides and ammonia in catalytic steam reforming - Google Patents

Process and plant for minimizing the emissions of nitrogen oxides and ammonia in catalytic steam reforming Download PDF

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Publication number
WO2018184731A1
WO2018184731A1 PCT/EP2018/025065 EP2018025065W WO2018184731A1 WO 2018184731 A1 WO2018184731 A1 WO 2018184731A1 EP 2018025065 W EP2018025065 W EP 2018025065W WO 2018184731 A1 WO2018184731 A1 WO 2018184731A1
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Prior art keywords
ammonia
condensate
gas
flue gas
steam reforming
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PCT/EP2018/025065
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French (fr)
Inventor
Sigrid Thole
Rafal Adamczyk
Maik Lehmann
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Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Original Assignee
Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
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    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/32Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air
    • C01B3/34Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents
    • C01B3/38Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents using catalysts
    • C01B3/384Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents using catalysts the catalyst being continuously externally heated
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/02Processes for making hydrogen or synthesis gas
    • C01B2203/0205Processes for making hydrogen or synthesis gas containing a reforming step
    • C01B2203/0227Processes for making hydrogen or synthesis gas containing a reforming step containing a catalytic reforming step
    • C01B2203/0233Processes for making hydrogen or synthesis gas containing a reforming step containing a catalytic reforming step the reforming step being a steam reforming step
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/04Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/04Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
    • C01B2203/0465Composition of the impurity
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/16Controlling the process
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/80Aspect of integrated processes for the production of hydrogen or synthesis gas not covered by groups C01B2203/02 - C01B2203/1695

Definitions

  • the invention relates to a process for minimizing the emission of nitrogen oxides and ammonia in the catalytic steam reforming of hydrocarbons to form synthesis gas, comprising the following process steps:
  • a steam reforming reactor which comprises a furnace space which is heated by burners (radiation zone) which are operated using the fuel gas, with formation of flue gas,
  • the invention further relates to a plant for carrying out the process.
  • Processes for producing synthesis gas containing hydrogen and carbon monoxide by means of catalytic steam reforming of a hydrocarbon-containing feed gas are known and described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, Vol. 15, Gas Production, Chapter 2.
  • the feed gases namely a hydrocarbon-containing gas, e.g. natural gas, and steam, hereinafter referred to as process steam, are passed at elevated pressure, e.g. from 20 to 35 bar, and elevated temperature, e.g. from 800 to 950 °C, through externally heated reactor tubes filled with catalyst.
  • the feed gases are here converted into hydrogen-rich and carbon monoxide-rich synthesis gas.
  • Such a reactor is frequently referred to as SMR and the process as SMR process, short for Steam Methane Reformer. It is very important for the economics of the process to utilize the heat of the synthesis gas exiting from the SMR and of the flue gas very effectively for preheating the feed gases and for generation of steam. In the subsequent cooling of the synthesis gas, part of the moisture present therein is condensed out.
  • the condensate formed here, hereinafter referred to as process condensate is, after removal of gaseous impurities, reused for generating process steam. Degassing is carried out purely physically, frequently by simple heating of the boiler feed water in a degassing apparatus, to form a condensate offgas stream.
  • This stream contains a mixture of volatile materials such as short-chain hydrocarbons, e.g. methanol, organic acids and ammonia.
  • volatile materials such as short-chain hydrocarbons, e.g. methanol, organic acids and ammonia.
  • the condensate offgas stream is frequently disposed of directly into the atmosphere, but because of the harm these materials cause to the environment and to health, alternative disposal methods have been considered for some time.
  • Laid-open publication DE 10 2007 059 542 A1 discloses a process in which the condensate offgas stream is fed into the hot flue gas stream from the steam reformer.
  • the introduction into the flue gas system should be carried out in such a way that the offgas stream is heated to a temperature in the range from 600 to 1050°C.
  • the free oxygen present in the flue gas oxidizes nitrogen-containing pollutants to nitrogen oxides, which can subsequently react further with ammonia which is still present to form free nitrogen and water vapour. This reaction is known as selective noncatalytic reduction (SNCR), which proceeds according to the following equation:
  • a further possibility mentioned is to mix part of the condensate offgas stream into the fuel gas.
  • a disadvantage of this process according to the prior art is that the success of the process, i.e. the very substantial destruction of the pollutants, depends mainly on the choice of the feed point for the condensate offgas stream.
  • the optimal feed point or combination of feed points has to be determined by experiments according to the principle of "trial and error". This procedure is very time-consuming and therefore costly.
  • An object of the invention is therefore to provide a corresponding process which can be installed with little difficulty in an SMR plant and leads to equivalent or improved results, especially in respect of the degradation of nitrogen-containing accompanying components such as ammonia.
  • Process for minimizing the emission of nitrogen oxides and ammonia in the catalytic steam reforming of hydrocarbons to form synthesis gas comprising the following process steps: a) providing a feed gas mixture comprising hydrocarbons and steam and a fuel gas comprising hydrocarbons and oxygen,
  • a steam reforming reactor which comprises a furnace space (radiation zone) which is heated by burners which are operated using the fuel gas, with formation of flue gas,
  • step e) the dividing and the addition in step e) are carried out in such a way that the concentration of the nitrogen oxides and/or of the ammonia in the flue gas is minimized.
  • Plant of the invention Plant of the invention:
  • Plant for minimizing the emission of nitrogen oxides and ammonia in the catalytic steam reforming of hydrocarbons to form synthesis gas comprising a steam reforming reactor, SMR, having a furnace space (radiation zone) equipped with burners operated using fuel gas and in which reactor tubes filled with catalyst are installed, further comprising a flue gas system for discharging the flue gas produced by the burners from the furnace space into the atmosphere, further comprising heat exchangers for cooling the synthesis gas exiting from the SMR and condensate separators for separating off the process condensate formed during cooling of the synthesis gas, further comprising a degassing apparatus in which the process condensate is degassed by heating or stripping to form a condensate offgas stream, further comprising apparatuses having pipes for feeding condensate offgas into the radiation zone and into the fuel gas, characterized in that the plant further comprises a regulating system comprising a regulating valve in each of the pipes of the apparatuses for feeding in condensate offgas,
  • steam reforming conditions are the process conditions known per se to a person skilled in the art, in particular temperature, pressure and residence time, as are mentioned by way of example above and explained in detail in the relevant literature and at which at least a partial conversion, but preferably industrially relevant conversions, of the starting materials into synthesis gas products such as CO and hydrogen occurs.
  • a catalyst which is active for steam reforming is a catalyst which brings about just such conversions under steam reforming conditions.
  • the invention makes use of the fact that an effective way of destroying ammonia is to allow it to react with nitrogen oxide according to the selective noncatalytic reduction described above.
  • part of the condensate offgas stream is fed into the fuel gas in order to convert the ammonia present therein into nitrogen oxide, according to the following equation :
  • the condensate offgas stream is divided between the fuelgas and the introduction into the combustion exhaust gas so that the nitrogen oxide content and the ammonia content in the burner exhaust gas released into the surroundings are minimized.
  • a preferred embodiment of the invention is characterized in that the substream of the condensate offgas provided for introduction into the flue gas in the radiation zone is divided into a plurality of further streams which are introduced into the radiation zone at different places. In this way, the mixing of the condensate offgas with the nitrogen oxide- containing flue gas and thus the destruction of the nitrogen oxides and of the ammonia by selective noncatalytic reduction can be optimized.
  • a further preferred embodiment of the invention is characterized in that the regulation of the nitrogen oxide content and of the ammonia content in the flue gas is carried out by means of an automatic regulating system. In this way, the division of the condensate offgas streams can be adapted quickly to changes and fluctuations in the steam reforming process.
  • Fig. 1 a plant flow diagram of an exemplary embodiment of the process of the invention and of the plant of the invention.
  • the plant 1 for catalytic steam reforming shown in Fig. 1 comprises a steam reforming reactor 2, SMR, having a furnace space 5 (radiation zone) which is equipped with burners 4 operated using fuel gas 3 and in which a plurality of reactor tubes 6 filled with catalyst are installed.
  • a steam reforming reactor 2 SMR, having a furnace space 5 (radiation zone) which is equipped with burners 4 operated using fuel gas 3 and in which a plurality of reactor tubes 6 filled with catalyst are installed.
  • preheated feed gas mixture 7 consisting of hydrocarbon-containing gas and process steam is converted into synthesis gas 8.
  • the steam reforming reactor 2 further comprises a flue gas system 9 for discharging the flue gas 10 produced by the burners 4 from the furnace space 5 into the atmosphere.
  • a heat exchanger 1 1 is installed in the flue gas system 9 in order to utilize the heat of the flue gas for the generation of steam.
  • the plant 1 comprises a system 12 consisting of a plurality of heat exchangers for cooling the synthesis gas 8 exiting from the SMR by heat exchange with the hydrocarbon-containing part of the feed gas and for generation of steam.
  • the synthesis gas 8 which has been cooled in the system 12 is discharged from the plant 1 for further treatment.
  • the ammonia-containing condensate 13 obtained in the system 12 from the synthesis gas 8 is introduced into the degassing system 14.
  • the degassed condensate 15 is used for generating process steam.
  • the ammonia-containing condensate offgas stream 16 produced in the degassing is divided into the streams 16a and 16b.
  • the substream 16a is in this example divided once more into two streams and is fed at two places into the furnace space 5 at which a temperature in the range from 1000 to 1060°C prevails.
  • Substream 16b is fed into the fuel gas 3.
  • the plant 1 is equipped with a regulating system which has a regulating valve 17a,b in each of the pipes for the substreams 16a,b of the condensate offgas 16, a measurement apparatus 18 installed in the flue gas system 9 for measuring the nitrogen oxide content and the ammonia content in the flue gas 10 and a computer system 19 which is able to receive the data from the measurement apparatus 18, evaluate these data and regulate the nitrogen oxide content and the ammonia content in the flue gas 10 in the direction of the minimum content possible in each case by appropriate actuation of the regulating valves 17a,b.
  • the invention makes it possible to minimize the emission of nitrogen oxide and ammonia from the steam reforming process with little expenditure of money.
  • the invention is therefore industrially applicable in an advantageous way.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Inorganic Chemistry (AREA)
  • Hydrogen, Water And Hydrids (AREA)

Abstract

Process and plant for carrying out the process for minimizing the emission of nitrogen oxides and ammonia in the catalytic steam reforming of hydrocarbons to form synthesis gas by introducing the offgas which contains these emissions and has been driven off from the process condensate partly into the fuel gas and partly into the radiation zone of the SMR reactor and decomposing the emissions by selective noncatalytic reduction.

Description

05.04.2017
AIR LIQUIDE File Number: 2016P00171
Process and plant for minimizing the emissions of nitrogen oxides and ammonia in catalytic steam reforming
Field of the invention
The invention relates to a process for minimizing the emission of nitrogen oxides and ammonia in the catalytic steam reforming of hydrocarbons to form synthesis gas, comprising the following process steps:
- providing a feed gas mixture comprising hydrocarbons and steam and a fuel gas comprising hydrocarbons and oxygen,
- converting the feed gas mixture into crude synthesis gas by catalytic steam reforming under steam reforming conditions in a steam reforming reactor which comprises a furnace space which is heated by burners (radiation zone) which are operated using the fuel gas, with formation of flue gas,
- cooling and drying the crude synthesis gas, with part of the moisture present therein being separated off therefrom to form an ammonia-containing process condensate,
- degassing the process condensate in a degassing apparatus to form an ammonia- containing condensate offgas stream,
- dividing the ammonia-containing condensate offgas stream into two substreams and adding the one substream to the burner gas and the other substream to the flue gas in the radiation zone,
- measuring the concentration of the nitrogen oxides and of the ammonia in the flue gas. The invention further relates to a plant for carrying out the process. Prior art
Processes for producing synthesis gas containing hydrogen and carbon monoxide by means of catalytic steam reforming of a hydrocarbon-containing feed gas are known and described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, Vol. 15, Gas Production, Chapter 2. The feed gases, namely a hydrocarbon-containing gas, e.g. natural gas, and steam, hereinafter referred to as process steam, are passed at elevated pressure, e.g. from 20 to 35 bar, and elevated temperature, e.g. from 800 to 950 °C, through externally heated reactor tubes filled with catalyst. The feed gases are here converted into hydrogen-rich and carbon monoxide-rich synthesis gas. Such a reactor is frequently referred to as SMR and the process as SMR process, short for Steam Methane Reformer. It is very important for the economics of the process to utilize the heat of the synthesis gas exiting from the SMR and of the flue gas very effectively for preheating the feed gases and for generation of steam. In the subsequent cooling of the synthesis gas, part of the moisture present therein is condensed out. The condensate formed here, hereinafter referred to as process condensate, is, after removal of gaseous impurities, reused for generating process steam. Degassing is carried out purely physically, frequently by simple heating of the boiler feed water in a degassing apparatus, to form a condensate offgas stream. This stream contains a mixture of volatile materials such as short-chain hydrocarbons, e.g. methanol, organic acids and ammonia. The condensate offgas stream is frequently disposed of directly into the atmosphere, but because of the harm these materials cause to the environment and to health, alternative disposal methods have been considered for some time.
Laid-open publication DE 10 2007 059 542 A1 discloses a process in which the condensate offgas stream is fed into the hot flue gas stream from the steam reformer. The introduction into the flue gas system should be carried out in such a way that the offgas stream is heated to a temperature in the range from 600 to 1050°C. The free oxygen present in the flue gas oxidizes nitrogen-containing pollutants to nitrogen oxides, which can subsequently react further with ammonia which is still present to form free nitrogen and water vapour. This reaction is known as selective noncatalytic reduction (SNCR), which proceeds according to the following equation:
2 NO + 2 NHs + 0.5 O2 <→ 2 N2 + 3 H2O
Many further possibilities for destroying the harmful materials present in the condensate offgas stream are proposed in the patent application US 2012/0051993 A1 . A plurality of feed points for the offgas stream into the burner exhaust gas system, and also into the furnace space of the SMR itself, are proposed. Here, a temperature of from 1000 to 1060°C should prevail at the feed point and it is said that a sufficient residence time of the harmful offgases in this temperature zone is necessary in order to destroy the materials.
A further possibility mentioned is to mix part of the condensate offgas stream into the fuel gas.
A disadvantage of this process according to the prior art is that the success of the process, i.e. the very substantial destruction of the pollutants, depends mainly on the choice of the feed point for the condensate offgas stream. The optimal feed point or combination of feed points has to be determined by experiments according to the principle of "trial and error". This procedure is very time-consuming and therefore costly.
An object of the invention is therefore to provide a corresponding process which can be installed with little difficulty in an SMR plant and leads to equivalent or improved results, especially in respect of the degradation of nitrogen-containing accompanying components such as ammonia.
Description of the invention
The object is achieved by a process having the features of Claim 1 and a plant having the features of Claim 4. Process of the invention :
Process for minimizing the emission of nitrogen oxides and ammonia in the catalytic steam reforming of hydrocarbons to form synthesis gas, comprising the following process steps: a) providing a feed gas mixture comprising hydrocarbons and steam and a fuel gas comprising hydrocarbons and oxygen,
b) converting the feed gas mixture into crude synthesis gas by catalytic steam reforming under steam reforming conditions in a steam reforming reactor which comprises a furnace space (radiation zone) which is heated by burners which are operated using the fuel gas, with formation of flue gas,
c) cooling and drying the crude synthesis gas, with part of the moisture present therein being separated off therefrom to form an ammonia-containing process condensate, d) degassing the process condensate in a degassing apparatus to form an ammonia- containing condensate offgas stream,
e) dividing the ammonia-containing condensate offgas stream into two substreams and adding the one substream to the fuel gas and the other substream to the flue gas in the radiation zone,
f) measuring the concentration of the nitrogen oxides and of the ammonia in the flue gas, wherein
g) the dividing and the addition in step e) are carried out in such a way that the concentration of the nitrogen oxides and/or of the ammonia in the flue gas is minimized.
Plant of the invention:
Plant for minimizing the emission of nitrogen oxides and ammonia in the catalytic steam reforming of hydrocarbons to form synthesis gas, comprising a steam reforming reactor, SMR, having a furnace space (radiation zone) equipped with burners operated using fuel gas and in which reactor tubes filled with catalyst are installed, further comprising a flue gas system for discharging the flue gas produced by the burners from the furnace space into the atmosphere, further comprising heat exchangers for cooling the synthesis gas exiting from the SMR and condensate separators for separating off the process condensate formed during cooling of the synthesis gas, further comprising a degassing apparatus in which the process condensate is degassed by heating or stripping to form a condensate offgas stream, further comprising apparatuses having pipes for feeding condensate offgas into the radiation zone and into the fuel gas, characterized in that the plant further comprises a regulating system comprising a regulating valve in each of the pipes of the apparatuses for feeding in condensate offgas, a measurement apparatus for measuring the nitrogen oxide content and the ammonia content in the flue gas installed in the flue gas system and an automatic regulator which is able to receive the data from the measurement apparatus, evaluate these data and regulate the nitrogen oxide content and the ammonia content in the direction of the minimum content possible in each case by appropriate actuation of the regulating valves. For the purposes of the present invention, steam reforming conditions are the process conditions known per se to a person skilled in the art, in particular temperature, pressure and residence time, as are mentioned by way of example above and explained in detail in the relevant literature and at which at least a partial conversion, but preferably industrially relevant conversions, of the starting materials into synthesis gas products such as CO and hydrogen occurs. Correspondingly, a catalyst which is active for steam reforming is a catalyst which brings about just such conversions under steam reforming conditions.
The invention makes use of the fact that an effective way of destroying ammonia is to allow it to react with nitrogen oxide according to the selective noncatalytic reduction described above.
To provide sufficient NOx for this reaction in the flue gas system, part of the condensate offgas stream is fed into the fuel gas in order to convert the ammonia present therein into nitrogen oxide, according to the following equation :
Figure imgf000007_0001
According to the invention, the condensate offgas stream is divided between the fuelgas and the introduction into the combustion exhaust gas so that the nitrogen oxide content and the ammonia content in the burner exhaust gas released into the surroundings are minimized. Preferred embodiments of the invention
A preferred embodiment of the invention is characterized in that the substream of the condensate offgas provided for introduction into the flue gas in the radiation zone is divided into a plurality of further streams which are introduced into the radiation zone at different places. In this way, the mixing of the condensate offgas with the nitrogen oxide- containing flue gas and thus the destruction of the nitrogen oxides and of the ammonia by selective noncatalytic reduction can be optimized. A further preferred embodiment of the invention is characterized in that the regulation of the nitrogen oxide content and of the ammonia content in the flue gas is carried out by means of an automatic regulating system. In this way, the division of the condensate offgas streams can be adapted quickly to changes and fluctuations in the steam reforming process.
Working example
Further features, advantages and possible uses of the invention can also be derived from the following description of a working and numerical example and the drawing. Here, all features described and/or depicted themselves or in any combination form the subject matter of the invention, regardless of the way in which they are summarized in the claims or their backreference.
The process of the invention will be illustrated below with the aid of the drawing. Here, the single figure shows
Fig. 1 a plant flow diagram of an exemplary embodiment of the process of the invention and of the plant of the invention.
The plant 1 for catalytic steam reforming shown in Fig. 1 comprises a steam reforming reactor 2, SMR, having a furnace space 5 (radiation zone) which is equipped with burners 4 operated using fuel gas 3 and in which a plurality of reactor tubes 6 filled with catalyst are installed. By way of example, only a single reactor tube 6 is shown in Fig. 1 . In the reactor tubes 6, preheated feed gas mixture 7 consisting of hydrocarbon-containing gas and process steam is converted into synthesis gas 8. The steam reforming reactor 2 further comprises a flue gas system 9 for discharging the flue gas 10 produced by the burners 4 from the furnace space 5 into the atmosphere. A heat exchanger 1 1 is installed in the flue gas system 9 in order to utilize the heat of the flue gas for the generation of steam. In addition, the plant 1 comprises a system 12 consisting of a plurality of heat exchangers for cooling the synthesis gas 8 exiting from the SMR by heat exchange with the hydrocarbon-containing part of the feed gas and for generation of steam. The synthesis gas 8 which has been cooled in the system 12 is discharged from the plant 1 for further treatment. The ammonia-containing condensate 13 obtained in the system 12 from the synthesis gas 8 is introduced into the degassing system 14. The degassed condensate 15 is used for generating process steam. The ammonia-containing condensate offgas stream 16 produced in the degassing is divided into the streams 16a and 16b. The substream 16a is in this example divided once more into two streams and is fed at two places into the furnace space 5 at which a temperature in the range from 1000 to 1060°C prevails. Substream 16b is fed into the fuel gas 3. In order to achieve a very low content of nitrogen oxide and ammonia in the offgas 10 released into the atmosphere, the plant 1 is equipped with a regulating system which has a regulating valve 17a,b in each of the pipes for the substreams 16a,b of the condensate offgas 16, a measurement apparatus 18 installed in the flue gas system 9 for measuring the nitrogen oxide content and the ammonia content in the flue gas 10 and a computer system 19 which is able to receive the data from the measurement apparatus 18, evaluate these data and regulate the nitrogen oxide content and the ammonia content in the flue gas 10 in the direction of the minimum content possible in each case by appropriate actuation of the regulating valves 17a,b.
Industrial applicability
The invention makes it possible to minimize the emission of nitrogen oxide and ammonia from the steam reforming process with little expenditure of money. The invention is therefore industrially applicable in an advantageous way. List of reference numerals
1 Plant of the invention
2 Steam reforming reactor, SMR
3 Fuel gas
4 Burners, with flames 4a
5 Furnace space
6 Reactor tubes
7 Feed gas mixture
8 Synthesis gas
9 Flue gas system
10 Flue gas
1 1 Heat exchanger
12 System of heat exchangers
13 Process condensate
14 Degassing system
15 Degassed process condensate
16 Condensate offgas stream, substreams 16a and 16b
17a,b Regulating valves
18 Measurement apparatus for measuring the nitrogen oxide content and ammonia content
19 Computer system

Claims

Claims:
1 . Process for minimizing the emission of nitrogen oxides and ammonia in the catalytic steam reforming of hydrocarbons to form synthesis gas, comprising the following process steps:
a) providing a feed gas mixture comprising hydrocarbons and steam and a fuel gas comprising hydrocarbons and oxygen,
b) converting the feed gas mixture into crude synthesis gas by catalytic steam reforming under steam reforming conditions in a steam reforming reactor which comprises a furnace space (radiation zone) which is heated by burners which are operated using the fuel gas, with formation of flue gas,
c) cooling and drying the crude synthesis gas, with part of the moisture present therein being separated off therefrom to form an ammonia-containing process condensate, d) degassing the process condensate in a degassing apparatus to form an ammonia- containing condensate offgas stream,
e) dividing the ammonia-containing condensate offgas stream into two substreams and adding the one substream to the fuel gas and the other substream to the flue gas in the radiation zone,
f) measuring the concentration of the nitrogen oxides and of the ammonia in the flue gas, characterized in that
g) the dividing and the addition in step e) are carried out in such a way that the concentration of the nitrogen oxides and/or of the ammonia in the flue gas is minimized.
2. Process according to Claim 1 , characterized in that the substream provided for introduction into the flue gas in the radiation zone is divided into a plurality of further streams which are introduced into the radiation zone at different places.
3. Process according to Claim 1 or 2, characterized in that the regulation of the nitrogen oxide content and of the ammonia content in the flue gas is carried out by means of an automatic regulating system.
4. Plant for performing the process according to Claim 3, comprising a steam reforming reactor, SMR, having a furnace space (radiation zone) equipped with burners operated using fuel gas and in which reactor tubes filled with catalyst are installed, further comprising a flue gas system for discharging the flue gas produced by the burners from the furnace space into the atmosphere, further comprising heat exchangers for cooling the synthesis gas exiting from the SMR and condensate separators for separating off the ammonia-containing process condensate formed during cooling of the synthesis gas, further comprising a degassing apparatus in which the process condensate is degassed by heating or stripping to form an ammonia-containing condensate offgas stream, further comprising apparatuses having pipes for feeding condensate offgas into the radiation zone and into the fuel gas, characterized in that the plant further comprises a regulating system comprising a regulating valve in each of the pipes of the apparatuses for feeding in condensate offgas, a measurement apparatus for measuring the nitrogen oxide content and the ammonia content in the flue gas installed in the flue gas system and an automatic regulator which is able to receive the data from the measurement apparatus, evaluate these data and regulate the nitrogen oxide content and the ammonia content in the direction of the minimum content possible in each case by appropriate actuation of the regulating valves.
PCT/EP2018/025065 2017-04-05 2018-03-21 Process and plant for minimizing the emissions of nitrogen oxides and ammonia in catalytic steam reforming Ceased WO2018184731A1 (en)

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EP4428094A1 (en) * 2023-03-07 2024-09-11 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Process and plant for producing a synthesis gas stream with minimum emission of ammonia
CN118738448B (en) * 2024-09-04 2024-11-01 福大紫金氢能科技股份有限公司 Cold exhaust power supply balance system using ammonia decomposition hydrogen production device

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