KR20240006365A - Carbon dioxide free ammonia decomposition plant - Google Patents

Abstract

The carbon dioxide-free ammonia decomposition facility according to the present invention is a carbon dioxide-free ammonia decomposition facility that produces hydrogen from ammonia, and includes a reformer that thermally decomposes ammonia gas to produce gas containing hydrogen and nitrogen; Cooling means for cooling the thermally decomposed gas by adiabatic expansion and condensing the undecomposed ammonia into liquefaction; Gas-liquid separation means for gas-liquid separation of liquid undecomposed ammonia from the cooled gas; and a PSA facility for removing nitrogen from the ammonia-removed gas. By including this, it is possible to reduce adsorbent regeneration and replacement costs compared to the conventional ammonia adsorption process by cooling, condensing and liquefying the undecomposed ammonia before the PSA process, and then separating the gas and liquid. In addition, fossil fuel is supplied from outside to decompose ammonia. It is possible to provide a hydrogen production facility without carbon dioxide emissions because only a mixed gas obtained by co-firing ammonia and the gas separated from the PSA facility (PSA tail gas) is used as a heat source.

Description

Carbon dioxide free ammonia decomposition plant {CARBON DIOXIDE FREE AMMONIA DECOMPOSITION PLANT}

The present invention relates to an ammonia decomposition plant for carbon dioxide-free hydrogen production.

Recently, climate change has worsened, and hydrogen energy has been attracting attention as an eco-friendly fuel used in place of fossil fuels around the world. For the practical use of hydrogen energy, it is important to develop technology to store and transport hydrogen safely and efficiently. There are several methods for storing hydrogen, but one method is to use a hydrogen storage material that can reversibly store and release hydrogen. It is expected to be used as a hydrogen storage medium for use in fuel cell vehicles.

Hydrogen has a very high energy density relative to weight (33.3 kWh/kg), but low energy density relative to volume (2.97 Wh/L, 0°C, 1 atm), so there is a need to increase energy density relative to volume by storing it in an appropriate manner. It is raised. In addition, safe and economical long-distance transportation technology for large-capacity hydrogen is essential to revitalize the hydrogen economy.

At the same time, it is essential to establish a domestic and international hydrogen supply chain ( _H2 supply chain) to safely supply large quantities of hydrogen, but if ultra-low-cost hydrogen produced overseas using renewable energy or unused fossil fuels is imported into Korea in large quantities, Due to the low energy storage density to volume of hydrogen, it is very difficult to transport it in the form of gaseous hydrogen.

Accordingly, in order to efficiently store and transport hydrogen, physical storage methods such as compressed hydrogen storage and liquefied hydrogen storage have been studied industrially, but these methods have problems such as safety and energy loss. For these reasons, interest in chemical storage methods that can stably transport and store large amounts of hydrogen is increasing.

Chemical hydrogen storage methods include liquid organic hydrogen carriers such as methanol (CH ₃ OH), sodium borohydride (NaBH ₄ ), ammonia borane (NH ₃ BH ₃ ), formic acid (HCOOH), and toluene (C ₇ H ₈ ). Organic Hydrogen Carrier (LOHC), etc. These materials inherently have many problems that need to be solved, such as low hydrogen storage capacity, high-cost processing (purification, etc.) systems, and high energy loss during hydrogen reproduction.

However, among chemical hydrogen storage methods, ammonia (NH ₃ ) is an ultra-high-capacity hydrogen storage/carrier with a storage capacity of 17.6 wt% and 120 kg-H ₂ /m ³ based on the weight and volume of the material, and can be used almost as is with existing storage and transportation infrastructure. It is attracting attention as a material that has the advantage of minimizing initial investment by utilizing it. In addition, unlike liquid organic hydrogen carriers (LOHC), ammonia does not contain carbon, so it does not emit substances with global warming problems such as carbon monoxide (CO) and carbon dioxide (CO ₂ ) after the dehydrogenation reaction, and is expressed in the following [Formula 1] As shown in the comparison of dehydrogenation energy in [ ], it is an alternative as an eco-friendly (green) material with the advantage of low ammonia dehydrogenation energy consumption.

[Formula 1]

C ₇ H ₁₄ → C ₇ H8 + 3H ₂ , ΔH = + 216.3 kJ/mol

2NH ₃ → N ₂ + 3H ₂ , ΔH = + 92.0 kJ/mol

However, the existing ammonia decomposition hydrogen production process requires a process to remove undecomposed ammonia and a PSA (pressure cycle adsorption method) process to remove decomposed N ₂ to produce high-purity hydrogen. The process of removing undecomposed ammonia generally uses an adsorbent to remove ammonia, but ammonia is difficult to regenerate after adsorption, making it difficult to select an adsorbent and configure a regeneration process. Additionally, the regeneration process requires a lot of energy, and high operating costs are expected due to frequent replacement of adsorbents. Furthermore, because fuels such as LNG or LPG are used to supply heat sources for ammonia reforming, carbon dioxide emissions cannot be avoided during the hydrogen production process.

Registration Patent No. 10-2178696 discloses an ammonia decomposition process, but only discloses a configuration using an adsorbent for undecomposed ammonia.

The ammonia decomposition facility of the present invention seeks to reduce operating costs by cooling, condensing, and liquefying undecomposed ammonia before the PSA process and then separating gas and liquid.

In addition, we aim to provide an ammonia decomposition facility without carbon dioxide emissions by co-firing ammonia and the gas separated from the PSA facility (PSA tail gas) as a heat source for the ammonia decomposition facility.

Equipment, comprising: a reformer that pyrolyzes ammonia gas to produce gas containing hydrogen and nitrogen; Cooling means for cooling the thermally decomposed gas by adiabatic expansion and condensing the undecomposed ammonia into liquefaction; Gas-liquid separation means for gas-liquid separation of liquid undecomposed ammonia from the cooled gas; and a PSA facility for removing nitrogen from the ammonia-removed gas. Provides a carbon dioxide-free ammonia decomposition facility containing.

It may further include a vaporizer that compresses and vaporizes liquid ammonia and supplies it to the reformer.

The reformer may pyrolyze the gas separated in the PSA facility (PSA tail gas) and ammonia by co-firing them as fuel.

The mole fraction of the gas separated in the PSA facility from the mixed gas may be 0.5 or more.

The reformer may perform thermal decomposition at a temperature of 400 to 700°C and a pressure of 15 to 200 Barg.

The cooling means may be an expansion turbine.

The gas-liquid separation means may be a deep cold separator.

The deep cold separator may separate gas and liquid at a temperature of -100 to -40°C and a pressure of 1-10 Barg.

At least a portion of the liquid undecomposed ammonia removed by the gas-liquid separation means can be supplied as fuel.

At least a portion of the liquid undecomposed ammonia removed by the gas-liquid separation means can be supplied as a source of ammonia.

The PSA equipment may remove nitrogen at a temperature of -50 to 40°C and a pressure of 0-10 Barg.

The reformer may include De-NO _x treatment equipment.

The ammonia decomposition facility of the present invention can reduce adsorbent regeneration costs and adsorbent replacement costs compared to the conventional ammonia adsorption process by cooling, condensing, and liquefying undecomposed ammonia before the PSA process and then separating gas and liquid.

In addition, it is possible to provide a hydrogen production facility without carbon dioxide emissions because it does not use fossil fuels supplied from outside to decompose ammonia and only uses a mixed gas obtained by co-firing ammonia and gas separated from the PSA facility as a heat source.

1 is a schematic diagram of an ammonia decomposition plant according to an embodiment of the present invention.
Figure 2 is a diagram showing simulation modeling of the ammonia decomposition facility of the present invention.
Figure 3 is a table summarizing the simulation results of the ammonia decomposition facility of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings. However, the embodiments of the present invention may be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Additionally, the embodiments of the present invention are provided to more completely explain the present invention to those with average knowledge in the relevant technical field. The shapes and sizes of elements in the drawings may be exaggerated for clearer explanation.

In addition, in this specification, singular expressions include plural expressions unless the context clearly indicates otherwise, and the same reference signs or reference signs assigned in a similar manner throughout the specification refer to the same or corresponding components. Let's do it.

Figure 1 is a schematic diagram of an ammonia decomposition facility according to an embodiment of the present invention, through which the decomposition facility of the present invention is explained in detail.

The present invention seeks to provide a carbon dioxide-free ammonia decomposition facility for separating hydrogen from ammonia, and more specifically, a reformer that thermally decomposes ammonia gas to produce a gas containing hydrogen and nitrogen; Cooling means for cooling the thermally decomposed gas by adiabatic expansion and condensing the undecomposed ammonia into liquefaction; Gas-liquid separation means for gas-liquid separation of liquid undecomposed ammonia from the cooled gas; and a PSA facility for removing nitrogen from the ammonia-removed gas.

First, the reformer pyrolyzes ammonia supplied from an ammonia source to emit hydrogen and nitrogen. A liquid pump can be used to supply ammonia from the ammonia source to the reformer, and the liquid pump can be of a diaphragm type, gear type, nonseal canned type, etc. In the case of liquid ammonia, because the viscosity is not high, there are no major limitations in selecting a pump, but the liquid pump must be of a non-pulsation type that can supply a fixed amount and minimize pulsation.

The reformer includes a main body having an internal space; a catalyst layer formed of catalysts in the internal space; an ammonia supply unit that supplies ammonia from the upper part of the main body to the internal space and moves the ammonia from the upper part of the internal space to the lower part; It is connected to the lower part of the main body, supplies a heat source to the lower part of the internal space, moves it to the upper part of the internal space, and moves it again to the lower part of the internal space, and is bent in a vertical direction to emit heat to the internal space. A heat source supply unit including piping; an exhaust gas discharge unit connected to the lower part of the main body and discharging exhaust gas, which is a heat source of heat loss, while moving from the upper part of the internal space to the lower part; and a mixing unit connected to the lower part of the main body, in which ammonia supplied to the upper part of the internal space moves down and passes through the catalyst layer, thereby discharging a mixed gas containing oxygen and nitrogen gas decomposed by heat and catalyst out of the main body. It may include a gas discharge unit.

The thermal decomposition reaction of ammonia occurring in the reformer is a reaction in which the number of moles after the reaction increases, as shown in the equation below, so the lower the pressure, the more the reaction is promoted. Since it is an endothermic reaction, the higher the temperature, the more the reaction is promoted. Therefore, in the reformer, thermal decomposition can proceed at a temperature of 400 to 700°C and a pressure of 15 to 200 Barg.

2NH ₃ → 3H ₂ + N _2, ΔH = +92.0kJ/mol

The heat source of the heat source supply part of the reformer may be co-fired with a mixed gas of ammonia and the tail gas separated in the PSA facility, which will be mentioned below, and the mole fraction of the gas separated in the PSA facility in the mixed gas may be 0.5 or more. Since the tail gas and ammonia do not contain carbon components, the exhaust gas does not contain carbon dioxide. The ammonia to be mixed may be ammonia supplied from an ammonia source or recycled undecomposed ammonia.

The catalyst layer of the reformer may further include a catalyst containing a metal or metal oxide, and the ammonia supplied to the reformer may be adsorbed on the surface of the catalyst and decomposed into hydrogen gas and nitrogen gas through an endothermic reaction and discharged.

The catalyst may be a known ammonia decomposition catalyst, and specifically, one or more elements selected from Ni, Pt, Pd, La, and Ru, or oxides containing the elements are used in Ce, Si, La, Ti, Mg, and Zr. One supported on a metal oxide support containing one or more selected metals may be used.

More specifically, the metal mixture selected from Ni/Pt, Ni/Pd, Ni/La2O3, and Ni/Ru as the ammonia decomposition catalyst includes one or more metals selected from Ce, Si, La, Ti, Mg, and Zr. Those supported on oxide supports can be used because they have a high ammonia decomposition rate.

As an example of the ammonia decomposition catalyst, an ammonia decomposition catalyst in which a coating layer containing a metal is additionally formed on a support can be used. The ammonia decomposition catalyst on which the coating layer is formed can improve the ammonia decomposition rate by improving the amount of catalyst supported and durability, The catalyst replacement cycle can be extended.

The reformer may further include a De-NO _x treatment facility in the exhaust gas discharge unit to reduce NO _x emissions of exhaust gas. The De-NO _x treatment facility is not particularly limited as long as it is a facility that removes nitrogen oxides.

The temperature of the exhaust gas is above 800°C, and the De-NO _x treatment facility normally removes nitrogen oxides at a temperature of 250 to 350°C. Therefore, the exhaust gas discharge unit including the De-NO _x treatment facility may further include a cooler to further lower the temperature of the exhaust gas.

The ammonia supplied to the reformer is preferably in gas form. At this time, a vaporizer may be further included between the ammonia source and the reformer to vaporize liquid ammonia and convert it into gaseous ammonia.

The vaporizer includes a heat source supply unit that vaporizes the supplied liquid ammonia into gas form; and an exhaust gas discharge unit that discharges exhaust gas, wherein the heat source of the vaporizer uses the same heat source as that of the reformer, so that the exhaust gas does not contain carbon dioxide.

The mixed gas discharged from the reformer is supplied to a cooling means. The mixed gas discharged after thermal decomposition in the reformer may contain nitrogen, hydrogen, and a trace amount of undecomposed ammonia, and among the mixed gas components, the boiling point of undecomposed ammonia is the highest at -33.34°C.

The cooling means liquefies only the undecomposed ammonia in the mixed gas. The cooling means can adiabatically expand the mixed gas supplied from the reformer to increase pressure and cool it. At this time, the process conditions of the cooling means are not particularly limited as long as the temperature and pressure are for liquefying the undecomposed ammonia, but when the temperature condition is -100 to -40°C and the pressure condition is 1-10 Barg, only the undecomposed ammonia is liquefied and separated. It can be.

The cooling means is not particularly limited as long as it is a facility that can cool high-temperature gas, but may be an expansion turbine.

The mixture of the mixed gas discharged from the cooling means and the liquefied undecomposed ammonia is supplied to the gas-liquid separation means. The gas-liquid separation means separates only the liquid undissolved ammonia separated in the cooling means from the mixture. Existing ammonia decomposition facilities used adsorbents in the PSA process to remove undecomposed ammonia, but ammonia has the characteristic of not being well regenerated after adsorption, so it has the disadvantage of making it difficult to select an adsorbent and configure a regeneration process. Accordingly, in order to remove undecomposed ammonia in the mixed gas, the present invention uses a cryogenic separator as a gas-liquid separation means to liquefy and separate the ammonia with the highest boiling point in the mixed gas before the PSA process, thereby producing a separate Since undecomposed ammonia can be separated without an adsorbent, it is easy to select an adsorbent and configure the regeneration process.

The temperature and pressure of the deep cooling separator are not particularly limited as long as it is for separating undecomposed ammonia from the mixed gas, but may be the same temperature and pressure as the cooling device, a temperature of -100 to -40°C and a pressure of 1-10 Barg. .

The liquid undecomposed ammonia removed by the gas-liquid separation means may be supplied as an ammonia source and then supplied back to the reformer, or may be mixed with the gas separated in the PSA facility mentioned below to be used as a heat source for the reformer.

Since the mixed gas from which the liquid undecomposed ammonia discharged from the gas-liquid separation means is removed is composed of nitrogen and hydrogen, it must undergo a hydrogen purification process to obtain high-purity hydrogen. Common purification methods include the pressure swing method (PSA method), the temperature swing method (TSA method) in which separation is performed by raising and lowering the temperature, or the pressure/temperature swing method in which the pressure and temperature are each swinged. The PSA method can be performed using a PSA facility.

The mixed gas from which the undecomposed ammonia is removed in the gas-liquid separation means is supplied to a PSA (Pressure Swing Adsorption) facility. The PSA facility has a pressure vessel filled with an adsorbent, uses the difference in the equilibrium adsorption amount or adsorption rate between the adsorbent and the mixed gas, and repeats adsorption and desorption through pressure fluctuations to adsorb nitrogen and purify and discharge high-purity hydrogen. there is.

The adsorbent used in the PSA equipment is not particularly limited, and materials widely known in the art such as zeolite or activated carbon can be used.

The mixed gas supplied to the PSA facility passes through a compressor, and nitrogen adsorption proceeds in the purification tower. When adsorption is completed, the pressure is relieved to desorb only the nitrogen in the mixed gas. The method of relieving the pressure is using a vacuum pump, and the desorption efficiency of nitrogen can be increased by using such a vacuum pump.

The temperature and pressure of the PSA equipment are not particularly limited, but may be a temperature condition of -50 to 40°C and a pressure condition of 0-10 Barg. It is supplied to the adsorption tower at a pressure of 0Barg or higher, and nitrogen can be desorbed by relieving the pressure when desorption is completed after adsorption.

Hereinafter, preferred embodiments of the present invention will be described with reference to various examples. However, the embodiments of the present invention may be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

Example

1. Simulation results of ammonia separation equipment

Figure 2 is a diagram showing simulation modeling of the ammonia decomposition facility of the present invention, and Figure 3 is a diagram showing the simulation results of the ammonia decomposition facility according to the present invention. The liquid ammonia supplied from the ammonia supplier is vaporized into a gas phase through a vaporizer, thermally decomposed in the reformer, and a mixed gas separated into nitrogen and hydrogen is produced. Undecomposed ammonia in the mixed gas is liquefied in the expansion turbine, and in a deep-cooled separator. Liquid ammonia is separated, and high-purity hydrogen can be obtained through PSA equipment.

According to Figure 3, the ammonia supplier stored ammonia with a mole fraction of 1.0000 at 25°C and 9.487 Barg, and supplied ammonia at 8,380 kg/h (13.60 m ³ /h).

Ammonia supplied from the ammonia supplier is supplied to the reformer through the same liquid pump, and at this time, the temperature of the reformer rises to 600℃ and the pressure rises to 97.5Barg. At this time, 75% of ammonia is thermally decomposed into hydrogen and nitrogen.

The mixed gas separated from the reformer is supplied to the expansion turbine, cooled to 20℃ under constant pressure conditions, and then adiabatically expanded in the expansion turbine under -75.34℃ and 6Barg process conditions to cool the undecomposed ammonia.

The mixture separated from the expansion turbine is supplied to a deep-cooled separator to separate the undecomposed ammonia. At this time, ammonia contained in the mixed gas discharged from the deep cooling separator is 1.08 mol% of the total mixed gas. The purity of ammonia separated in the deep-cooled separator is 0.9999%, and is supplied to the ammonia feeder or mixed with the gas separated in the PSA facility.

The mixed gas discharged from the deep cooling separator is heated isobarically and supplied to the PSA facility under process conditions of 30℃ and 5.9Barg to separate hydrogen and nitrogen.

According to Figure 3, the hydrogen extracted from the PSA facility has a temperature of 30.09°C, a pressure of 5.687Barg, a purity of 1.0, and 999kg/h (11,104 Nm ³ /h).

2. Measurement of carbon dioxide content in exhaust gas

The components of the exhaust gas discharged from the exhaust gas outlet of the reformer were measured. As a heat source for the reformer, a mixed gas of 7,369 kg/hr, which was a mixture of ammonia and gas separated from the PSA facility at a molar ratio of 1:3, was co-fired and used, and a De-NO _x treatment facility was placed.

As a result of the measurement, the reformer exhaust gas contains N ₂ , H ₂ O, NO, etc., but does not contain carbon dioxide. The concentration of nitrogen oxides in the exhaust gas supplied to the De-NOx treatment facility is about 400ppm.

Although representative embodiments of the present invention have been described in detail above, those skilled in the art will understand that various modifications can be made to the above-described embodiments without departing from the scope of the present invention. . Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the patent claims described later as well as equivalents to these claims.

Claims (12)

A carbon dioxide-free ammonia decomposition facility that produces hydrogen from ammonia,
A reformer that pyrolyzes ammonia gas to produce gas containing hydrogen and nitrogen;
Cooling means for cooling the thermally decomposed gas by adiabatic expansion and condensing the undecomposed ammonia into liquefaction;
Gas-liquid separation means for gas-liquid separation of liquid undecomposed ammonia from the cooled gas; and
PSA equipment for removing nitrogen from the ammonia-removed gas;
Carbon dioxide-free ammonia decomposition plant containing. According to paragraph 1,
A carbon dioxide-free ammonia decomposition facility further comprising a vaporizer that compresses and vaporizes liquid ammonia and supplies it to the reformer. According to paragraph 1,
The reformer is a carbon dioxide-free ammonia decomposition facility that thermally decomposes the gas separated from the PSA facility (PSA tail gas) and ammonia by co-firing them as fuel. According to paragraph 3,
A carbon dioxide-free ammonia decomposition facility in which the mole fraction of the gas separated from the mixed gas in the PSA facility is 0.5 or more. According to paragraph 1,
The reformer is a carbon dioxide-free ammonia decomposition facility that thermally decomposes at a temperature of 400 to 700 ° C. and a pressure of 15 to 200 Barg. According to paragraph 1,
The cooling means is a carbon dioxide-free ammonia decomposition facility using an expansion turbine. According to paragraph 1,
The gas-liquid separation means is a carbon dioxide-free ammonia decomposition facility that is a deep cooling separator. In clause 7,
The deep-cooled separator is a carbon dioxide-free ammonia decomposition facility that separates gas and liquid at a temperature of -100 to -40 ℃ and a pressure of 1-10 Barg. According to clause 8,
A carbon dioxide-free ammonia decomposition facility that supplies at least a portion of the liquid undecomposed ammonia removed by the gas-liquid separation means as fuel. According to paragraph 1,
A carbon dioxide-free ammonia decomposition facility that supplies at least a portion of the liquid undecomposed ammonia removed by the gas-liquid separation means as a source of ammonia. According to paragraph 1,
The PSA facility is a carbon dioxide-free ammonia decomposition facility that removes nitrogen under a temperature of -50 to 40°C and a pressure of 0-10Barg. According to paragraph 1,
The reformer is a carbon dioxide-free ammonia decomposition facility including a De-NO _x treatment facility.