KR20230166744A - Method of producing hydrogen and ethanol using steel by-product gas - Google Patents

Abstract

The present invention includes the steps of (a) mixing blast furnace gas (BFG) and converter gas (LDG), which are by-product gases generated in the steelmaking process; (b) adding LNG to the by-product gas and preheating it; (c) supplying the BFG, LDG, and LNG composite gas to a composite reformer to convert it into a reducing gas containing CO and H ₂ through a double reforming reaction (Bi-reforming reaction); (d) cooling the reducing gas by supplying cooling water; (e) extracting high purity H ₂ from the cooled reducing gas and supplying the remaining tail gas to an ethanol fermentor; (f) fermenting ethanol using CO in the ethanol fermentor; and (g) capturing CO ₂ in the residual gas remaining after fermenting ethanol, and injecting the gas from which CO ₂ has been removed into the combustion unit of the combined reformer to utilize it as fuel. Hydrogen and ethanol using steel by-product gas including. A manufacturing method is provided.

Description

Method of producing hydrogen and ethanol using steel by-product gas {Method of producing hydrogen and ethanol using steel by-product gas}

The present invention relates to a method for producing hydrogen and ethanol using steel by-product gas, and more specifically, to a method for efficiently producing hydrogen and ethanol from by-product gas including LNG and BFG and LPG.

With the launch of the new climate system, Korea needs to reduce greenhouse gas emissions from by-product gases in the steel industry in order to achieve the 37% reduction target compared to the 2030 emissions forecast (BAU). In integrated steel mills, by-product gases such as coke oven gas (COG), blast furnace gas (BFG), and converter gas (LDG) are generated during processing processes such as coke ovens, blast furnaces, and converters. Steel by-product gas contains a large amount of carbon dioxide and also contains large amounts of carbon monoxide and hydrogen that can be used as a heat source. It is estimated that by-product gas contains about 20 million tons of carbon monoxide, which is a high value-added resource, and about 1 million tons of hydrogen, but only a small portion of this is actually recovered.

Carbon monoxide contained in by-product gas can be synthesized into alcohols including ethanol through hydrogenation reaction, and the synthesized ethanol is used as a solvent and fuel as a basic raw material in the chemical industry, and can be converted into high value-added chemical products through additional processes. Conversion is possible. In other words, if CO, the main component of by-product gas, is converted into useful chemicals, higher economic efficiency can be secured compared to existing petrochemical processes.

Meanwhile, COG, which contains a large amount of hydrogen among by-product gases, is used to obtain hydrogen through Pressure Swing Absorption (PSA) and is used as a reducing gas in the steelmaking process. However, in addition to hydrogen, COG contains methane and carbon monoxide as main components, so when reducing gases such as hydrogen are extracted directly from COG itself, not only is the extraction efficiency low, but also the production of large quantities of reduced gas requires a large-capacity process. There is a problem that equipment investment must be accompanied.

The present invention is intended to solve various problems including the above problems, and seeks to develop a process that can increase the value of by-product gas by producing hydrogen and ethanol by effectively utilizing the by-product gas of steelmaking.

However, these tasks are illustrative and do not limit the scope of the present invention.

According to an embodiment of the present invention, a method for producing hydrogen and ethanol using steel by-product gas is provided. The manufacturing method includes (a) mixing blast furnace gas (BFG) and converter gas (LDG), which are by-product gases generated in the steelmaking process, (b) adding LNG to the by-product gas and preheating, (c) Supplying the BFG, LDG, and LNG composite gas to a composite reformer to convert it into a reducing gas containing CO and H ₂ through a double reforming reaction, (d) supplying cooling water to the reducing gas Cooling step, (e) extracting high purity H ₂ from the cooled reduction gas and supplying the remaining tail gas to the ethanol fermenter, (f) fermenting ethanol using CO in the ethanol fermenter, and (g) ) It includes the step of collecting CO ₂ in the residual gas remaining after fermenting ethanol, and injecting the gas from which CO ₂ has been removed into the combustion section of the combined reformer to use it as fuel.

In one embodiment, the flow rate ratio of BFG, LDG, and LNG in the composite gas may be (BFG + LDG):LNG = 65:35 to 55:45.

In one embodiment, after step (d), the step of introducing water vapor generated by cooling the reducing gas into the preheating process (b) may be further included.

In one embodiment, the combined reformer combustion unit may include a burner housing to enable continuous combustion of the combined gas.

In one embodiment, the reaction temperature of the Bi-reforming reaction may be 800 to 1000°C.

In one embodiment, step (e) may be extracting the high purity H ₂ through a hydrogen pressure swing adsorption (PSA) process.

In one embodiment, in step (g), the gas introduced into the combustion unit of the combined reformer may include CO and H ₂ .

In one embodiment, in step (b), the CH ₄ /CO _x (x=1 or 2) ratio may be 0.5 to 1.5.

In one embodiment, the step of capturing carbon dioxide in step (g) includes recovering and separating carbon dioxide using a chemical absorption or adsorption method to capture more than 95% of carbon dioxide; and a purification step of removing moisture, acidic substances, corrosive substances and salt-generating substances from the captured carbon dioxide to obtain carbon dioxide with a purity of 99.5% or more.

In one embodiment, step (f) may be a step of converting tail gas containing CO into ethanol by fermenting it with microorganisms.

According to an embodiment of the present invention as described above, a product containing hydrogen and high value-added alcohol is produced using steel mill by-product gas and LNG, thereby reducing CO ₂ greenhouse gases and converting carbon into resources. In addition, it has the effect of maximizing hydrogen and carbon monoxide production by optimizing the temperature within the process and simultaneously recycling the generated water vapor to the complex reforming. Additionally, by recirculating the residual gas after carbon dioxide capture, the operating efficiency of the reforming process can be improved and profitability can be increased.

Of course, the scope of the present invention is not limited by this effect.

Figure 1 is a schematic diagram of a method for producing hydrogen and carbon monoxide using steel by-product gas according to an embodiment of the present invention.
Figure 2 is a schematic structure of a reformer according to an embodiment of the present invention.
Figure 3 is a schematic diagram of a bioethanol fermentation process according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings. 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 art. Accordingly, the shapes and sizes of elements in the drawings may be exaggerated for clearer explanation, and elements indicated by the same symbol in the drawings are the same elements.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

Figure 1 is a schematic diagram of a method for producing hydrogen and ethanol using steel by-product gas according to an embodiment of the present invention. The present invention produces CO and H ₂ through a catalytic reaction using LNG and by-product gas raw materials, generates and supplies water vapor using the heat generated during the reaction, and produces high-purity hydrogen through the H ₂ PSA process and uses the remaining gas as a bio-process. This relates to technology for producing ethanol through fermentation.

The present invention will be described in detail with reference to FIG. 1 as follows.

First, blast furnace gas (BFG) and converter gas (LDG), which are by-product gases generated in the steelmaking process, are injected into the gas mixer 10 and mixed. BLAST FURNACE GAS (BFG) is obtained as a by-product gas in the blast furnace of a steel mill, and most of the pig iron generated in the blast furnace is converted to steel in a basic oxygen furnace. At this time, the converter gas ( Linz-Donawitz Converter Gas (LDG) is obtained. Blast furnace gas (BFG) and converter gas (LDG) contain CO and CO ₂ as main components, and the approximate volumes of the components are shown in Tables 1 and 2 below.

BFG Ingredients _CO2 C.O. H ₂ N ₂ Content (volume%) 21 22 3 54

LDG composition _CO2 C.O. N2 Others (H ₂ , O ₂ ) Content (volume%) 18 64 16 2

Among by-product gases, converter gas (LDG) has a characteristic that the flow rate fluctuates greatly depending on the steel operation conditions, and blast furnace gas (BFG) has a characteristic that it contains a lot of N ₂ , an inert gas. In one embodiment, LDG is preferentially introduced into the gas mixer 10 based on the CO and CO ₂ concentrations required for the reaction, and when the LDG flow rate changes, BFG may be added as an alternative fuel to compensate for the shortfall.

Next, LNG (liquefied natural gas) is additionally injected into the LDG and BFG by-product gas mixture and preheated in the gas preheater 20.

The main component of LNG gas fuel is CH ₄ and the specific composition is shown in Table 3 below.

LNG component CH ₄ C ₂ H ₆ C ₃ H ₈ etc Content (volume%) 91.4 5.3 2.4 0.9

The gas preheater 20 is installed in front of the composite reformer 30, which will be described later, and can raise the temperature of the composite gas input to the composite reformer 30. Preferably, fuel usage can be minimized by raising the temperature of the composite gas to about 400°C. Unlike a typical gas heat exchanger, the gas preheater 20 may be provided to provide a space in which fuel gas and water vapor are mixed and preheated. As shown in Equation 1, which will be described later, in the reaction between CH ₄ and CO ₂ , the reduction gas conversion reaction proceeds at a molar ratio of CH ₄ : CO ₂ = 3:1. That is, by adding LNG to the by-product gas mixture to satisfy CH ₄ :CO ₂ =3:1, a raw material gas composition suitable for the reduction gas conversion reaction can be obtained. However, the molar ratio between CH ₄ and CO ₂ is not particularly limited, and may be adjusted appropriately so that the CH ₄ /CO ₂ ratio is in the range of 1 to 5.

When by-product gas and LNG are mixed so that CH ₄ :CO ₂ = 3:1 according to the component ratios shown in Tables 1 to 3, the ratio of CH ₄ /CO _x (x = 1 or 2) in the composite gas is 0.5 It can meet the range of 1.5 to 1.5. For example, when the ratio of CH ₄ /CO _x (x=1 or 2) is 0.5, the mixing ratio of byproduct gas and LNG may be 62.9% and 37.1%. For example, when the CH ₄ /CO _x (x=1 or 2) ratio is 1.5, the mixing ratio of byproduct gas and LNG may be 59% and 41%. However, the CH ₄ /CO _x (x=1 or 2) ratio in the complex gas may vary depending on process operating conditions or by-product gas flow rate.

The preheated BFG, LDG, and LNG composite gas is supplied to the composite reformer 30 to undergo a double reforming reaction (Bi-reforming reaction). Bi-reforming reaction is a process in which natural gas and steam are converted into a high-temperature reduced gas containing CO and H ₂ by reacting according to the reaction equation below.

<Equation 1>

3CH ₄ + CO ₂ + 2H ₂ O → 4CO + 8H ₂

In forming a reducing gas, the flow rate ratio of BFG + LDG and LNG mixed to satisfy the molar ratio of (BFG + LDG) and LNG = 1:3 may be 65%: 35%) to 55%: 45%. In addition, when the ratio of BFG + LDG and LNG satisfies the above range based on the molar ratio of the reducing gas, a raw material gas composition suitable for conversion to reducing gas can be provided. Since the double reforming reaction causes a strong endothermic reaction, an external supply of reaction heat is required. For example, the reaction can be performed under high temperature conditions of 800°C to 1000°C. The optimal concentration of CO ₂ to optimize the amount of reducing gas produced under these temperature conditions may be, for example, 10 to 20% by volume based on the total volume of the complex gas.

Figure 2 is a schematic structure of a composite reformer 30 according to an embodiment of the present invention. The composite reformer 30 may have burner housings (gas burners) sealed in a cylindrical shape within a furnace. The burner burns fuel to generate exhaust gas and heats the reaction tube. The burner housing may be prepared to enable continuous combustion by mixing gases with different calorific values. For example, the burner may have the characteristic of burning BFG and LDG, which have low calorific value, and simultaneously burning LNG, which has high calorific value. This allows combustion to be tailored to the characteristics of each fuel, improving combustion efficiency and smoothly recovering CO and H ₂ gas.

Inside the complex reformer 30, a plurality of reaction tubes (reformer tubes) where reforming reactions occur may be installed vertically. The catalyst used in the double reforming reaction is contained in the reaction tube and may be, for example, a catalyst containing Ni, preferably a catalyst containing Ni-Co, but is not limited thereto. The double reforming reaction may be performed, for example, under pressure conditions of 1 to 5 kgf/Cm ² . Flue gas discharged from the furnace may be transferred to a convection section and exchange heat with natural gas and water vapor.

Since the double reforming reaction has high temperature reaction conditions (800°C to 1000°C), it is necessary to cool the gas in order to input it into the H2 PSA process, which will be described later. Preferably, cooling water (water) is put into the gas cooler 40 and cooled to about 40°C. At this time, the cooling water is converted into steam through heat exchange with the gas, and the converted steam can be input into the gas preheater 20. By recycling steam as fuel for reforming reactions, it is possible to achieve the effect of securing not only productivity but also economic efficiency of the overall process.

Next, high purity (99.999%) H ₂ is extracted from the cooled reducing gas. High purity H ₂ can be selectively extracted from a pressure swing adsorption (PSA) device 50 through a hydrogen extraction process. The hydrogen PSA is a process technology that adsorbs and removes impurities under high pressure to purify hydrogen from a mixed gas containing hydrogen to high purity, and the pressure is lowered when the adsorbed material is desorbed and regenerated. In the PSA gas separation system, different adsorbents are used depending on the gas to be separated. Adsorbents that can be used in H ₂ PSA for hydrogen separation include, but are not limited to, PSA CMS (Carbon Molecular Sieve), zeolite, etc. Any adsorbent that can independently adsorb hydrogen can be used. The high purity H ₂ extracted in this way can be used as fuel for fuel cell vehicles or power generation, thereby realizing economic effects.

Next, the step of extracting H ₂ as described above and supplying the remaining tail gas to the ethanol fermenter is performed. Tail gas refers to the gas remaining after H ₂ is extracted from the pressure swing adsorption (PSA: Pressure Swing Adsorption) device 50, and the tail gas is discharged discontinuously or continuously. Therefore, it is desirable to include a step of collecting it so that it can be used. For example, a low-pressure storage vessel can be used to collect the tail gas. The tail gas contains H ₂ as a main component, and may further include one or more selected from the group consisting of CO, CO ₂ , and N ₂ . In particular, the content of H ₂ contained in the tail gas can be determined depending on the hydrogen recovery rate recovered through the hydrogen extraction process. When the hydrogen extraction process produces high purity of 99%, the hydrogen recovery rate may be, for example, 50 to 80%, and in this case, H ₂ may be 20 to 40% by volume based on the total volume of the tail gas.

Next, the step of fermenting ethanol using CO is performed in an ethanol reactor. Figure 3 is a schematic diagram of the bioethanol fermentation process. Tail gas containing CO flows into the ethanol fermenter 60 through gas treatment and pressure boosting, and ethanol is produced through microbial reaction as shown in Equation 2 below. During microbial fermentation, carbon capture efficiency can be improved by applying a certain current to improve ethanol production performance as needed. If carbon dioxide is produced with a high purity of 95-99.5%, the CO conversion rate can be 90%.

<Equation 2>

6CO + 3 H ₂ O -> C ₂ H ₂ OH (ethanol) + 4CO ₂

The produced ethanol goes through a purification facility and is sold as high-purity ethanol. The steam generated here can be recycled as energy needed during the process to improve process efficiency. The residual gas remaining after producing ethanol can be utilized by collecting carbon dioxide and then inputting it into the complex reformer (30). Ethanol is an eco-friendly biofuel that replaces fossil fuels, and according to the embodiment of the present invention as described above, ethanol can be produced using by-product gas from the steelmaking process, making it environmentally friendly.

The residual gas remaining after fermenting ethanol may include CO ₂ , N ₂ , CO and H ₂ . The residual gas is input into the carbon dioxide capture device (70). The step of capturing carbon dioxide can be done using a wet process using an amine absorbent. Amines that can be used at this time are not limited to these, but include monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), methyldiethanolamine (MDEA), 2-amino-2-methyl-1- Propanol, etc. can be mentioned. By removing moisture, acidic substances, corrosive substances and salt-generating substances present in the carbon dioxide captured by the above method, carbon dioxide with a purity of 99.5% or more can be obtained. The gas from which CO ₂ has been removed may include CO and H ₂ . The gas from which CO ₂ has been removed can be used as fuel by inputting it into the combustion section of the combined reformer (30).

According to the embodiment of the present invention as described above, the hydrogen economy can be revitalized by recycling hydrogen from steel by-product gas and stably supplying hydrogen to hydrogen fuel electric vehicles, power plants, etc. In addition, CO, the main component of by-product gas, can be converted into ethanol, ensuring higher economic efficiency compared to existing petrochemical processes. According to an embodiment of the present invention, there is an effect of maximizing CO and H ₂ production by injecting water vapor generated during the process into the complex reforming process. In addition, by recirculating the residual gas from which carbon dioxide has been removed into the complex reforming process, the operating efficiency of the reforming process can be improved and profitability can be increased.

The terms used in the present invention are for describing specific embodiments and are not intended to limit the present invention. Unless it is clear from the context, singular expressions should be considered to have a plural meaning. Terms such as “include” or “have” mean that features, numbers, steps, operations, components, or combinations thereof described in the specification exist, but are not intended to exclude them. The present invention is not limited by the above-described embodiments and attached drawings, but is intended to be limited by the attached claims. Accordingly, various forms of substitution, modification, and change may be made by those skilled in the art without departing from the technical spirit of the present invention as set forth in the claims, and this also falls within the scope of the present invention. something to do.

10: Gas mixer
20: Gas preheater
30: Complex reformer
40: gas cooler
50: Pressure swing adsorption (PSA) device
60: Ethanol fermenter
70: Carbon dioxide capture device

Claims (10)

(a) mixing blast furnace gas (BFG) and converter gas (LDG), which are by-product gases generated in the steelmaking process;
(b) adding LNG to the by-product gas and preheating it;
(c) supplying the BFG, LDG, and LNG composite gas to a composite reformer to convert it into a reduction gas containing CO and H ₂ through a double reforming reaction (Bi-reforming reaction);
(d) cooling the reducing gas by supplying cooling water;
(e) extracting high purity H ₂ from the cooled reducing gas and supplying the remaining tail gas to an ethanol fermentor;
(f) fermenting ethanol using CO in the ethanol fermentor; and
(g) collecting CO ₂ in the residual gas remaining after fermenting ethanol, and injecting the gas from which CO ₂ has been removed into the combustion unit of the combined reformer;
Method for producing hydrogen and ethanol using steel by-product gas. In clause 1
The flow ratio of BFG, LDG and LNG in the composite gas is (BFG + LDG): LNG = 65:35 to 55:45,
Manufacturing method for producing hydrogen and ethanol using steel by-product gas. According to claim 1,
After step (d), it further includes the step of introducing water vapor generated by cooling the reducing gas into (b) the preheating process,
Method for producing hydrogen and ethanol using steel by-product gas. According to claim 1,
The combined reformer combustion section,
Comprising a burner housing to enable continuous combustion of the composite gas,
Method for producing hydrogen and ethanol using steel by-product gas. According to clause 1,
The reaction temperature of the Bi-reforming reaction is 800 to 1000°C,
Method for producing hydrogen and ethanol using steel by-product gas. According to claim 1,
The step (e) is
Extracting the high purity H ₂ through a hydrogen pressure swing adsorption process (PSA),
Method for producing hydrogen and ethanol using steel by-product gas. According to claim 1,
In step (g) above,
The gas introduced into the combustion section of the combined reformer contains CO and H ₂ .
Method for producing hydrogen and ethanol using steel by-product gas. According to claim 1,
In step (b) above,
CH ₄ /CO _x (x=1 or 2) ratio is 0.5 to 1.5,
Method for producing hydrogen and ethanol using steel by-product gas. According to claim 1,
The step of capturing carbon dioxide in step (g) is,
Recovering and separating carbon dioxide using a chemical absorption method to capture more than 95% of carbon dioxide; and
Including a purification step of removing moisture, acidic substances, corrosive substances and salt-generating substances from the captured carbon dioxide to obtain carbon dioxide with a purity of 99.5% or more.
Method for producing hydrogen and ethanol using steel by-product gas. According to claim 1,
In step (f),
This is the step of converting tail gas containing CO into ethanol by fermenting it with microorganisms.
Method for producing hydrogen and ethanol using steel by-product gas.