JP2008222480A - Method for synthesizing ammonia - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for synthesizing ammonia by which ammonia can be efficiently synthesized with low fuel consumption using an inexpensive solid raw material. <P>SOLUTION: A steam added gas 17 fed to an autothermal reformer 19 is fed to a heat exchange furnace 31 into which combustion exhaust gas 5 of a fluidized bed combustion furnace 1 is introduced, and the steam added gas is heated to a required reforming temperature by heat exchange. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ammonia synthesis method, and in particular, it is possible to synthesize ammonia with low fuel consumption cost and high efficiency by using inexpensive solid raw materials such as coal (including low quality coal such as lignite), biomass, and super heavy oil. The present invention relates to a method for synthesizing ammonia.

In recent years, various plants for synthesizing ammonia have been constructed. Typically, hydrogen is produced from a hydrocarbon raw material using natural gas, and ammonia is synthesized by synthesizing the hydrogen and nitrogen. ing. FIG. 6 is a flow sheet showing an outline of an example thereof. Steam is mixed with a hydrocarbon raw material a of natural gas (mainly methane CH ₄ ) and supplied to a steam reformer b. The reforming is performed according to the reaction formula I.

CH ₄ + H ₂ O → CO + 3H ₂ (I)
Shift reaction (side reaction): (CO + H ₂ O ← → CO ₂ + H ₂ ) (II)

  Next, air is mixed with the reformed gas obtained and supplied to an autothermal reformer c (ATR = autothermal reformer), and the remaining hydrocarbons in the presence of air are mainly used in the following reaction formulas III and III. Modified by IV.

2CH ₄ + O ₂ → 2CO + 4H ₂ (exothermic reaction) (III)

CH ₄ + H ₂ O → CO + 3H ₂ (endothermic reaction) (IV)
Shift reaction (side reaction): (CO + H ₂ O ← → CO ₂ + H ₂ ) (V)

  Subsequently, the reformed gas is supplied to the shift reactor d whose temperature is controlled, and the carbon dioxide produced by the reaction of changing the carbon monoxide by the shift reaction of Formula V to carbon dioxide is separated. As a result, most of the reformed gas is only hydrogen and nitrogen by the air supply, and ammonia is produced by supplying the hydrogen and nitrogen to the ammonia synthesis reactor e. The ammonia synthesis reactor e is generally operated so that the ratio of hydrogen to nitrogen (HN ratio) is about 3. A plant in which ammonia is produced using a hydrocarbon raw material such as natural gas is disclosed in Patent Document 1, for example.

On the other hand, instead of using expensive natural gas as a raw material, a gasified gas containing hydrocarbon CH ₄ is produced by gasifying using a solid raw material such as coal, and ammonia is produced using this gasified gas. An apparatus for synthesizing is considered.

  FIG. 7 shows an example. In the figure, 1 is a fluidized bed combustion furnace, 2 is a fluidized bed gasification furnace, and the fluidized bed combustion furnace 1 introduces char and fluidizes and burns it with air A. Heat the fluid medium. The high-temperature fluid 3 discharged from the fluidized bed combustion furnace 1 is guided to the separator 4 and separated into the combustion exhaust gas 5 and the fluidized medium 6.

The fluidized bed gasification furnace 2 is supplied with a high-temperature fluidized medium 6 separated by the separator 4 and a solid raw material 7 such as coal, and is further supplied with a gasifying agent from the lower part of the fluidized bed gasification furnace 2. As a result, the solid raw material 7 is gasified by supplying and fluidizing the water vapor S as a gasification mixture of hydrocarbons such as methane CH ₄ , hydrogen H ₂ , carbon monoxide CO, and carbon dioxide CO ₂ . Gas 8 is produced. Further, the char and the fluid medium generated when the solid 7 is gasified in the fluidized bed gasification furnace 2 are supplied to the fluidized bed combustion furnace 1 through the circulation channel 9. The air A supplied to the fluidized bed combustion furnace 1 is air exchanged with the combustion exhaust gas 5 by the heat exchanger 29, and the steam S supplied to the fluidized bed gasification furnace 2 is heated. Steam obtained by exchanging heat between the combustion exhaust gas 5 and water by the exchanger 30 is used.

  The gasification gas 8 taken out from the fluidized bed gasification furnace 2 is removed from the tar and the like by the gas purifier 10 and is pressurized by the booster 11, and then a heating furnace provided with a burner 12 for burning gas fuel and the like. 13 for heating. That is, the gasification gas 8 is first heated by the heating unit 14 to the operating temperature of the catalyst of the desulfurization device 15 (for example, around 400 to 500 ° C.) and guided to the desulfurization device 15 for desulfurization. Further, the desulfurized gasified gas 8 is mixed with steam 16, and the steam-added gas 17 is led again to the heating unit 18 of the heating furnace 13 and the required reforming temperature of the autothermal reformer 19 (for example, 700 ° C.). And then supplied to the autothermal reformer 19.

  Further, the air 20 obtained by pressurizing the air 20 with the booster 21 is heated to a required temperature by the heating unit 22 of the heating furnace 13 and then supplied to the self-heat reformer 19. At this time, the temperature of the air 20 supplied to the autothermal reformer 19 may be the same as the required reforming temperature (for example, around 700 ° C.) or may be lower.

In the autothermal reformer 19, reactions according to the above reaction formulas I, II, and III are performed, and a reformed gas 23 containing hydrogen H ₂ , nitrogen N ₂ , and carbon components (CO, CO ₂ ) is generated.

  The temperature of the reformed gas 23 is lowered by the first temperature controller 24 and led to the high temperature shift reaction means 25, and the temperature is further lowered by the second temperature regulator 26 and led to the low temperature shift reaction means 27. Carbon monoxide in the reformed gas 23 is converted to carbon dioxide and removed.

Hydrogen H ₂ and nitrogen N ₂ from which carbon components have been removed by the high temperature shift reaction means 25 and the low temperature shift reaction means 27 are supplied to the ammonia synthesis reactor 28 to synthesize ammonia.

Furthermore, Patent Document 2 discloses that gasified gas is generated by an oxygen gasification method (partial oxidation method) in which coal or coke is used as a raw material to react with oxygen and water vapor, and then hydrocarbons in the gasified gas are modified. There is a method in which ammonia is produced from a reformed gas obtained by reforming using a quality device.
JP 09-165215 A Japanese Patent Laid-Open No. 60-011587

  When ammonia is synthesized using gasified gas 8 obtained by gasification from solid raw material 7 such as coal as in the method shown in FIG. 7, sulfur is removed by introducing gasified gas 8 to desulfurization device 15. There is a need to. For this reason, the gasification gas 8 needs to be led to the heating furnace 13 and first heated to the operating temperature of the catalyst (for example, around 400 to 500 ° C.). On the other hand, since the gasification gas 8 from which sulfur has been removed by the desulfurization apparatus 15 needs to be mixed with the steam 16 for steam reforming in the autothermal reformer 19, the steam-added gas 17 in which the steam 16 is mixed. The temperature drops to around 100 ° C. Therefore, it is necessary to raise the temperature of the steam-added gas 17 again to the required reforming temperature of the self-heat reformer 19 (for example, around 700 ° C.). For this purpose, the steam-added gas 17 is led to the heating furnace 13 and heated.

  However, since the heating furnace 13 that heats the gasified gas 8 and the steam-added gas 17 is heated by burning a fuel such as gas in the burner 12, there is a problem that the fuel consumption cost of the heating furnace 13 increases. is there. In particular, in order to reheat the steam-added gas 17 whose temperature has dropped to around 100 ° C. by mixing the steam 16 to around 700 ° C., which is the required reforming temperature of the self-thermal reformer 19, for example, it is very much It is necessary to burn the fuel. Further, in order to increase the production amount of ammonia, when the supply amount of the solid raw material 7 to the fluidized bed gasification furnace 2 is increased to increase the generation amount of the gasification gas 8, it is consumed in the heating furnace 13. There is a problem that the fuel is further increased, and thus the cost for producing ammonia is greatly increased.

  Moreover, as shown in Patent Document 2, in the oxygen gasification method in which coal or coke is reacted with oxygen and water vapor to generate gasified gas, an oxygen generator for producing oxygen from air is expensive, and There is a problem that the operating cost also increases.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an ammonia synthesis method in which ammonia can be synthesized with high efficiency at low fuel consumption cost using an inexpensive solid raw material.

The invention of claim 1 heats the fluidized medium by introducing and burning char into the fluidized bed combustion furnace,
The high-temperature fluid discharged from the fluidized bed combustion furnace is guided to a separator and separated into combustion exhaust gas and fluidized medium,
The separated high-temperature fluidized medium is introduced into a fluidized bed gasification furnace to gasify the solid raw material with water vapor to generate gasified gas, and the char and fluidized medium generated when the solid raw material is gasified are fluidized bed. Circulating to the combustion furnace,
A steam-added gas obtained by mixing steam with gasified gas generated in a fluidized bed gasifier is heated to the required reforming temperature and supplied to the autothermal reformer, and air is supplied to reform the hydrocarbons in the gas. And
The reformed gas of the autothermal reformer is led to the high temperature shift reaction means and the low temperature shift reaction means to remove the carbon component in the reformed gas,
An ammonia synthesis method for producing ammonia by supplying the obtained hydrogen and nitrogen to an ammonia synthesis reactor,
A method for synthesizing ammonia, wherein the steam-added gas supplied to the autothermal reformer is heated to a required reforming temperature by using heat of a fluidized bed combustion furnace.

  In the above ammonia synthesis method, the combustion exhaust gas discharged from the fluidized bed combustion furnace and separated by the separator is supplied to the heat exchange furnace to exchange heat with the steam addition gas, thereby changing the steam addition gas to the required reforming temperature. It is preferable to heat it to the

  In the ammonia synthesis method, the steam-added gas is heated to a reforming required temperature by supplying the steam-added gas to a heat exchange means provided in the fluidized-bed combustion furnace and exchanging heat with the fluidized-bed combustion furnace. preferable.

  In the above ammonia synthesis method, it is preferable to exchange heat between the reformed gas and water at the inlet of the high temperature shift reaction means and supply the obtained water vapor to the fluidized bed gasifier as gasification water vapor.

  In the above ammonia synthesis method, it is preferable that heat is exchanged between the reformed gas and air at the inlet of the low temperature shift reaction means, and the obtained air is supplied to the fluidized bed combustion furnace as combustion air.

  According to the ammonia synthesis method of the present invention, the steam-added gas supplied to the autothermal reformer is heated to the required reforming temperature using the heat of the fluidized bed combustion furnace. Compared with the method of heating in a furnace heated by combustion, the fuel consumption cost by the burner can be greatly reduced, and therefore ammonia can be synthesized with low fuel consumption cost and high efficiency by using cheap solid materials such as coal. An excellent effect can be achieved.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a flow sheet showing an embodiment of the present invention applied to the apparatus shown in FIG. 7. In FIG. 1, the same reference numerals denote the same members. Only will be described in detail.

  As shown in FIG. 1, solid fuel 7 such as coal is supplied to a fluidized bed gasification furnace 2 to gasify it, and the char generated during gasification is circulated to the fluidized bed combustion furnace 1 together with a fluidized medium to burn the char. In the facility for heating the fluidized medium by the above and synthesizing ammonia using the gasified gas 8 from the fluidized bed gasification furnace 2, the high temperature fluid 3 discharged from the fluidized bed combustion furnace 1 is converted into the combustion exhaust gas 5 and the fluidized medium 6. The high-temperature combustion exhaust gas 5 from the separator 4 that is to be separated is supplied to the heat exchange furnace 31. The heat exchange furnace 31 includes a heating unit 14 that heats the gasification gas 8 supplied to the desulfurization device 15 by heat exchange with the combustion exhaust gas 5, and a steam addition gas 17 supplied to the self-heat reformer 19. And a heating unit 22 that heats the air 20 supplied to the self-heat reformer 19 by heat exchange with the combustion exhaust gas 5. Here, the temperature of the combustion exhaust gas 5 discharged from the fluidized bed combustion furnace 1 when coal is gasified in the fluidized bed gasification furnace 2 is maintained at a high temperature of, for example, about 900 to 1000 ° C.

  Further, a heat exchanger 32 for exchanging heat between the reformed gas 23 and water is provided at the inlet of the high temperature shift reaction means 25 in FIG. 1, and the steam S obtained by the heat exchange is supplied to the fluidized bed gasification furnace 2 for gasification. It is made to supply as water vapor. A heat exchanger 33 for exchanging heat between the reformed gas 23 and air is provided at the inlet of the low temperature shift reaction means 27, and the air A obtained by the heat exchange is supplied to the fluidized bed combustion furnace 1 as combustion air. I am doing so.

  The operation of the embodiment shown in FIG. 1 will be described below.

  The combustion exhaust gas 5 derived from the fluidized bed combustion furnace 1 has a high temperature of about 900 to 1000 ° C. and is discharged in a large amount, so that the combustion exhaust gas 5 has a very large amount of heat.

  Accordingly, when the steam-added gas 17 whose temperature has been reduced by mixing the steam 16 is supplied to the heating unit 18 of the heat exchange furnace 31, the self-heat reformer 19 requires the combustion exhaust gas 5 introduced into the heat exchange furnace 31. It can be easily heated to the required reforming temperature of around 700 ° C. Furthermore, since the amount of heat retained by the combustion exhaust gas 5 is sufficiently large, it is easy to heat the gasified gas 8 to the operating temperature of the catalyst of the desulfurization device 15 (for example, around 400 to 500 ° C.) by the heating unit 14 and air. It is also easy to heat 20 to the temperature supplied to the self-heat reformer 19 by the heating unit 22.

  At this time, the temperature of the steam addition gas 17 supplied to the autothermal reformer 19, the temperature of the gasification gas 8 supplied to the desulfurization device 15, and the temperature of the air 20 supplied to the autothermal reformer 19 are exchanged. The heat transfer area of each heating unit 18, 14, 22 to be performed can be adjusted, and the shape of the heat exchange furnace 31 is changed, or the combustion exhaust gas 5 introduced into the heat exchange furnace 31 is introduced. Adjustments can be made with changes such as changing the position.

  As described above, the steam-added gas 17 supplied to the self-heat reformer 19 is heated to the required reforming temperature using the heat of the combustion exhaust gas 5 introduced into the heat exchange furnace 31, so Compared to the method of heating the steam-added gas in a heating furnace using burner combustion, the amount of fuel used can be greatly reduced. Therefore, using low-cost solid materials such as coal, high efficiency with low fuel consumption cost Ammonia can be synthesized.

  In addition, the steam S obtained by providing the heat exchanger 32 for exchanging heat between the reformed gas 23 and water at the inlet of the high temperature shift reaction means 25 is supplied to the fluidized bed gasification furnace 2 as gasification steam, Since the air A obtained by providing the heat exchanger 33 for exchanging heat between the reformed gas 23 and air at the inlet of the low temperature shift reaction means 27 is supplied to the fluidized bed combustion furnace 1 as combustion air originally. Since it is necessary to cool and lower the temperature of the reformed gas 23 at the inlets of the high temperature shift reaction means 25 and the low temperature shift reaction means 27, the steam for reforming is used by using the heat corresponding to the temperature drop of the reformed gas 23. S and combustion air A can be obtained, and energy can be used effectively.

  FIG. 2 is a flow sheet showing another embodiment of the present invention. In this embodiment, a heat exchange channel 34 through which the steam-added gas 17 is circulated is provided on the entire outer periphery or part of the fluidized bed combustion furnace 1. An integrally formed heat exchange means 35 is provided, and the steam-added gas 17 mixed with the steam 16 is passed through the heat-exchange channel 34 to be heated to the required reforming temperature. The heat reformer 19 is supplied.

  As the heat exchanging means 35, as shown in FIG. 2, a heat exchanging channel 34 is integrally provided outside the fluidized bed combustion furnace 1, as shown in FIG. A method of integrally forming the flow path 36, or a method of disposing a heat transfer flow path 37 along the outer surface of the fluidized bed combustion furnace 1 and covering the outside with an outer wall 38, as shown in FIG. As shown in FIG. 5, a method of disposing a heat transfer passage 39 inside the fluidized bed combustion furnace 1 may be adopted.

  In the embodiment of FIG. 2, a heating furnace 40 for heating the gasified gas 8 supplied to the desulfurization device 15 by the heating unit 14 and heating the air 20 supplied to the self-heat reformer 19 by the heating unit 22 is provided. The heating furnace 40 is provided with a burner 41 for heating. The heating furnace 40 is for heating the gasified gas 8 supplied to the desulfurization apparatus 15 and the air 20 supplied to the self-heat reformer 19, and the amount of heat for heating them is determined by the addition of steam. The amount of heat for heating the gas 17 to around 700 ° C., which is the required reforming temperature, is very small, so that the fuel consumption of the burner 41 is very small.

  2, the steam S obtained by providing the heat exchanger 32 for heat exchange between the reformed gas 23 and water at the inlet of the high temperature shift reaction means 25 is gasified into the fluidized bed gasification furnace 2. The air A obtained by providing a heat exchanger 33 for heat exchange between the reformed gas 23 and air at the inlet of the low temperature shift reaction means 27 is supplied to the fluidized bed combustion furnace 1 as combustion air. You may make it do. In this way, the heat removal for heating the gasification steam S and the combustion air A can be omitted from the combustion exhaust gas 5 at the outlet of the separator 4, so the heat of the combustion exhaust gas 5 from the separator 4 can be reduced. All can be used for steam generation of the boiler at the latter stage.

  The operation of the embodiment shown in FIG. 2 will be described below.

  The internal temperature of the fluidized bed combustion furnace 1 is normally maintained at a high temperature of about 900 to 1200 ° C. Therefore, when the steam-added gas 17 is passed through the heat exchange means 35 provided in the fluidized bed combustion furnace 1, the steam 16 is The steam-added gas 17 whose temperature has been reduced by mixing is easily heated to the required reforming temperature of about 700 ° C. required by the autothermal reformer 19.

  At this time, the temperature of the steam addition gas 17 can be adjusted by selecting the heat transfer area of the heat exchange means 35 provided in the fluidized bed combustion furnace 1.

  Further, the gasification gas 8 supplied to the desulfurization apparatus 15 is heated by, for example, about 400 to 500 ° C. by the heating unit 14 provided in the heating furnace 40, and the air 20 supplied to the self-heat reformer 19 is provided in the heating furnace 40. The heating unit 22 is heated to a predetermined temperature. In this heating furnace 40, the amount of heat for heating the gasification gas 8 supplied to the desulfurization device 15 and the amount of heat for heating the air 20 supplied to the self-heat reformer 19 are set so that the steam-added gas 17 has the required reforming temperature. Since it is very small compared to the amount of heat heated to around 700 ° C., the amount of fuel consumed by the burner 41 can be kept very small.

  It should be noted that the ammonia synthesis method of the present invention is not limited to the above embodiment, and it is needless to say that various modifications can be made without departing from the scope of the present invention.

It is a flow sheet of an example which carries out the present invention. It is a flow sheet of another example which carries out the present invention. It is a schematic side view which shows the other example of the heat exchange means with which the fluidized bed combustion furnace was equipped. It is a schematic side view which shows the further another example of the heat exchange means with which the fluidized bed combustion furnace was equipped. It is a schematic side view which shows the further another example of the heat exchange means with which the fluidized bed combustion furnace was equipped. It is a flow sheet which shows an example of the conventional which manufactures ammonia using natural gas. It is a flow sheet which shows an example of the past which manufactures ammonia from gasification gas generated using a solid material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluidized bed combustion furnace 2 Fluidized bed gasification furnace 3 High temperature fluid 4 Separator 5 Combustion exhaust gas 6 Fluid medium 7 Solid raw material 8 Gasification gas 16 Steam 17 Steam addition gas 19 Self-heat reformer 20 Air 23 Reforming gas 25 High temperature Shift reaction means 27 Low temperature shift reaction means 28 Ammonia synthesis reactor 32 Heat exchanger 33 Heat exchanger 35 Heat exchange means A Air S Steam

Claims (5)

Heating the fluidized medium by introducing char into the fluidized bed combustion furnace and burning it,
The high-temperature fluid discharged from the fluidized bed combustion furnace is guided to a separator and separated into combustion exhaust gas and fluidized medium,
The separated high-temperature fluidized medium is introduced into a fluidized bed gasification furnace to gasify the solid raw material with water vapor to generate gasified gas, and the char and fluidized medium generated when the solid raw material is gasified are fluidized bed. Circulating to the combustion furnace,
A steam-added gas obtained by mixing steam with gasified gas generated in a fluidized bed gasifier is heated to the required reforming temperature and supplied to the autothermal reformer, and air is supplied to reform the hydrocarbons in the gas. And
The reformed gas of the autothermal reformer is led to the high temperature shift reaction means and the low temperature shift reaction means to remove the carbon component in the reformed gas,
An ammonia synthesis method for producing ammonia by supplying the obtained hydrogen and nitrogen to an ammonia synthesis reactor,
A method of synthesizing ammonia, comprising heating a steam-added gas supplied to the self-heat reformer to a required reforming temperature using heat of a fluidized bed combustion furnace.   Combustion exhaust gas discharged from the fluidized bed combustion furnace and separated by a separator is supplied to a heat exchange furnace to exchange heat with the steam addition gas, thereby heating the steam addition gas to the required reforming temperature. The ammonia synthesis method according to claim 1.   The steam addition gas is heated to a required reforming temperature by supplying the steam addition gas to a heat exchange means provided in a fluidized bed combustion furnace and exchanging heat with the fluidized bed combustion furnace. A method for synthesizing ammonia.   Heat exchange is performed between the reformed gas and water at the inlet of the high temperature shift reaction means, and the obtained steam is supplied to the fluidized bed gasification furnace as steam for gasification. A method for synthesizing ammonia.   The reformed gas and air at the inlet of the low temperature shift reaction means are subjected to heat exchange, and the obtained air is supplied to the fluidized bed combustion furnace as combustion air. The ammonia synthesis method described.

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