KR20110076103A - Method for producing ammonia and method for producing urea using converter gas - Google Patents

Abstract

The present invention relates to a method for producing a low-cost ammonia or urea using a converter gas generated in a large amount in the steelmaking process, and more particularly, by supplying water to the converter gas, which is a steelmaking process gas, and supplied water with carbon monoxide in the converter gas. Water gas conversion step of producing a hydrogen and carbon dioxide by catalytic reaction; A carbon dioxide separation step of separating and removing the produced carbon dioxide; A methanation step of removing the carbon monoxide and carbon dioxide by reacting the carbon dioxide of carbon monoxide remaining in the converter gas with the hydrogen to methanate; And ammonia production step by Haber-Bosch process using a catalyst of Fe-containing compound at 150-250atm / 300-550 ° C as a raw material using hydrogen obtained in the water gas shift reaction of carbon monoxide and the converter gas. A method for producing ammonia from a gas and a method for producing urea by reacting carbon dioxide and ammonia produced therefrom are provided.

Urea, Ammonia, Converter Gas, Carbon Dioxide, Carbon Monoxide, Hydrogen, Methanation

Description

METHODS FOR PRODUCING AMMONIA AND UREA BY USING THE CONVERTER GAS}

The present invention relates to a method for producing inexpensive ammonia or urea using converter gas generated in a large amount in a steelmaking process.

At present, a general ammonia production process is produced according to the process sequence as shown in Figure 1 using a natural gas such as methane, liquefied petroleum gas such as propane or butane or petroleum naphtha as a raw material. That is, first, the hydrocarbon-based raw material goes through a desulfurization process (H ₂ + RSH → RH + H ₂ S), and then hydrogen and carbon monoxide are produced through a steam reforming reaction. At this time, the steam reforming reaction using methane is shown in the following scheme 1.

CH ₄ + H ₂ O → 3H ₂ + CO ΔH = +49.3 kcal / mol (1)

Next, a water-gas shift reaction is performed to remove carbon monoxide and increase hydrogen, which is shown in Scheme 2 below.

CO + H ₂ O → CO ₂ + H ₂ ΔH = -9.8 kcal / mol (2)

Carbon dioxide is separated and removed by chemical absorption using ethanolamine aqueous solution or PSA (Pressure Swing Adsorption) adsorption using a solid adsorbent.

And a small amount of residual carbon monoxide and carbon dioxide is removed by methanation using a catalyst. Such methanation reaction can be represented by the following schemes 3 and 4.

CO + 3H ₂ → CH ₄ + H ₂ O (3)

CO ₂ + 4H ₂ → CH ₄ + 2H ₂ O (4)

Thus, the produced hydrogen is ammonia produced through a catalytic reaction with nitrogen introduced from the air. The reaction of obtaining such ammonia is shown in Scheme 5.

3H ₂ + N ₂ → 2NH ₃ (5)

As can be seen from the reaction schemes (1) to (5), various steps must be taken to obtain hydrogen and nitrogen, which requires a lot of energy. In particular, the reforming process requires expensive equipment, and also requires a process of matching hydrogen / nitrogen ratio through air injection. This causes a higher ammonia manufacturing cost.

In addition, the production cost is unstable as the carbon source is related to the international energy price as the petroleum extract in the production of urea, and the price of urea changes according to the energy price.

As described above, the conventional urea manufacturing process produces hydrogen and carbon dioxide through a reforming reaction of hydrocarbons (LNG, naphtha, etc.) and a water gas shift reaction, and after separating carbon dioxide from the mixed gas, hydrogen and nitrogen are mixed with nitrogen. After reacting to form ammonia, the separated and recovered carbon dioxide is reacted with the prepared ammonia to prepare urea. However, in the case of producing ammonia and urea by this method, the equipment cost required for the hydrocarbon reforming process is high, and the operating cost is high due to the energy cost required for the process.

Table 1 below shows the components of the converter gas which is the exhaust gas of the steelmaking process. As can be seen from Table 1, the converter gas generated in a large amount in the steelmaking process contains about 65% of the high concentration of carbon monoxide, and the converter gas contains an appropriate amount of nitrogen for producing ammonia.

TABLE 1

Furtherance LDG (vol%) CO ₂ 17.8 CO 64.4 H ₂ 2.0 N ₂ 15.8

Therefore, the present invention can be used to produce hydrogen through a water gas conversion reaction using the carbon monoxide of the converter gas, and then use it in the ammonia production process, and additional nitrogen or air as a nitrogen source is required for the process of additional input The invention is completed with the focus on not being able to.

Accordingly, the present invention does not require a reforming process of hydrocarbons using a converter gas generated in a large amount in the steelmaking process as a carbon source, and therefore, an object of the present invention is to provide a method for producing ammonia or urea at low cost.

In order to achieve at least the above object, the present invention provides a hydrogen / nitrogen ratio suitable for ammonia production by reacting carbon monoxide in the converter gas, which is an iron making process exhaust gas, with water, removing carbon dioxide, and removing residual carbon monoxide and carbon dioxide by methanation reaction. To make raw materials with

As a first embodiment, an aqueous gas conversion step of producing hydrogen and carbon dioxide by catalyzing carbon monoxide and supplied water in a converter gas by supplying water to a converter gas which is a steelmaking process gas; A carbon dioxide separation step of separating and removing the produced carbon dioxide; A methanation step of removing the carbon monoxide and carbon dioxide by reacting the carbon dioxide of carbon monoxide remaining in the converter gas with the hydrogen to methanate; And ammonia manufacturing step by a Haber-Bosch process using Fe-containing compound catalyst at 150-250atm / 300-550 ° C as a raw material of hydrogen and nitrogen contained in the converter gas obtained from the water gas shift reaction of carbon monoxide. Method for producing ammonia from

As a second embodiment, the carbon dioxide separation step is a method for producing ammonia from the converter gas is to remove impurities in the carbon dioxide and purified to carbon dioxide having a purity of at least 99.5%,

As a third embodiment, the catalyst used in the water gas conversion step is a method for producing ammonia from a converter gas which is a catalyst of Fe or Cu-containing compounds, and

As a fourth embodiment, the carbon dioxide separation step is a method for producing ammonia from the converter gas to separate the carbon dioxide by a chemical absorption method using an aqueous ethanolamine solution or a pressure swing adsorption (PSA) adsorption method using a solid adsorbent,

As a fifth embodiment, the carbon dioxide separation step is a method for producing ammonia from the converter gas is to separate the carbon dioxide by chemical absorption method using a ethanolamine aqueous solution or PSA adsorption method using a solid adsorbent, and the like,

As a sixth embodiment, there is provided a method for producing urea by reacting ammonia produced by the method with carbon dioxide obtained from the carbon dioxide separation step to produce urea.

By manufacturing ammonia raw materials using converter gas, which is the exhaust gas of the steelmaking process, production costs can be lowered compared to the ammonia manufacturing process using natural gas such as methane, LPG such as propane or butane or petroleum naphtha, and high energy. The reforming step that requires can be omitted, thereby reducing energy consumption.

In addition, carbon dioxide released into the atmosphere can be reduced by utilizing carbon dioxide, which is abundant in the converter gas, as a carbon source required for the production of urea by a chemical immobilization method.

Furthermore, there is an advantage that can stabilize the production cost through the diversification of the existing ammonia manufacturing raw material.

The converter gas, which is the exhaust gas of the steelmaking process to be used in the present invention, contains a large amount of carbon monoxide as described above, and has a relatively high nitrogen content.

Accordingly, the present invention is a method of producing a mixed gas having a reaction equivalent ratio of 3 to a suitable hydrogen / nitrogen as a raw material for ammonia production through the conversion of water gas, carbon dioxide removal, and methanation to the converter gas, which is a large amount of flue gas generated in the steelmaking process. To provide. In addition, the present invention provides a method for producing urea using the ammonia produced and carbon dioxide separated and recovered in the ammonia manufacturing process.

Since the ammonia production method of the present invention uses hydrogen, carbon monoxide and carbon dioxide in the exhaust gas, unlike the case of using conventional hydrocarbons, no reforming process is required, and the carbon monoxide present in the converter exhaust gas is catalytically reacted with water to form hydrogen. And a water gas conversion step for producing carbon dioxide. This water gas conversion step is the same as the water gas conversion step used in the prior art, when water is supplied to the converter exhaust gas stream, the water and carbon monoxide supplied as shown in the following equation (2) reacts to produce hydrogen and carbon dioxide.

CO + H ₂ O → CO ₂ + H ₂ ΔH = -9.8 kcal / mol (2)

The content of the supplied water can be changed according to the content of carbon monoxide, but the volume ratio of carbon monoxide and water is usually 4: 1 to 1: 1, more preferably 3.5: 1 to 2: 1, most preferably 3 Moisture can be supplied to have a ratio of 1: 1.

The reaction catalyst that can be used at this time may include a catalyst of Fe or Cu-containing compounds, more specifically, but not limited to this, Fe ₃ O, Cr ₂ O ₃ / Fe ₃ O as a catalyst of the Fe-containing compound _And CuO / Cr ₂ O ₃ / Fe ₃ O _4. Cu-based catalysts include Cu / ZnO, Cu / ZrO ₂ , and Cu / ZnO / Al ₂ O ₃ .

Next, the carbon dioxide produced here is separated and recovered. The carbon dioxide recovered here is then used to make urea by reaction with the ammonia produced later.

The carbon dioxide used in making the urea is required to have the specifications as described in Table 2 below.

TABLE 2

Item Remarks Carbon dioxide purity 99.5% or more Possible Impurities Up to 0.5% moisture and inert gases (nitrogen, argon, hydrogen, methane, etc.) Insoluble substances Acid, corrosive, salt generating materials, etc.

Therefore, it is preferable to purify the produced carbon dioxide to have a specification of carbon dioxide suitable for urea production after separation and recovery.

First, the carbon dioxide present after the water gas conversion from the converter flue gas is separated and recovered from the flue gas stream. In this case, the separation and recovery method may be used without limitation as long as it is a method commonly used in the art to which the present invention pertains. Specifically, a chemical absorption method using an ethanol amine aqueous solution or a PSA (Pressure Swing Adsorption) adsorption method using a solid adsorbent may be used. Can be collected using

The carbon dioxide thus collected may include impurities present in the converter flue gas. As shown in Table 2 above, even impurities, such as water or an inert gas, do not adversely affect the urea manufacturing process. Although it is allowed to contain up to volume%, acidic, corrosive, salt generating materials, etc. adversely affect the production of urea, and should not remain in carbon dioxide.

Therefore, it is preferable to purify the collected carbon dioxide to have a purity of 99.5% or more. The method for purifying the carbon dioxide may be applied to a purification method commonly used in the art.

Thereby removing the remaining carbon monoxide and carbon dioxide from the converter off-gas from which carbon dioxide has been removed. Methanation reaction can be applied to the removal of carbon monoxide and carbon dioxide. The methanation reaction of the present invention can form methane even without using a catalyst unlike the prior art.

CO + 3H ₂ → CH ₄ + H ₂ O (3)

CO ₂ + 4H ₂ → CH ₄ + 2H ₂ O (4)

By this methanation step, most of the carbon monoxide and carbon dioxide present in the converter gas can be removed.

Thus, hydrogen generated in the water gas conversion step and nitrogen present in the converter flue gas react through a catalytic reaction to produce ammonia. The reaction of obtaining such ammonia is shown in Scheme 5.

3H ₂ + N ₂ → 2NH ₃ (5)

This reaction can be carried out by the methods commonly used in the production of ammonia. For example, ammonia may be produced using a conventionally used Haber-Bosch process, and at this time, the pressure and temperature are not particularly limited, but 150-250 atm and 300-550 ° C. may be mentioned. Nitrogen and hydrogen can synthesize ammonia most efficiently when they have a value of 3 in the volume ratio of hydrogen / nitrogen.

For the ammonia production, a catalyst commonly used in the production of ammonia can be used, and examples thereof include an Fe-based catalyst.

Furthermore, the step of reacting the synthesized ammonia with the purified carbon dioxide to produce a urea. Such component manufacture can be performed using methods commonly used in the art.

Example

Example  One

Cr and Fe nitrate were co-precipitated to 10% Cr ₂ O ₃ and then calcined with a mixed gas containing 400 ° C. to prepare Fe ₃ O ₄ / Cr ₂ O ₃ for HTS (High temperature shift).

Coprecipitation was carried out using an aqueous solution of Cu and Zn metal nitrate and sodium carbonate so that the Cu / Zn ratio was 0.8, and then impregnated in Al ₂ O ₃ to 30 wt% CuO, 55 wt% ZnO, and 15 wt% Al ₂ O _3. Cu-Zn / Al ₂ O ₃ catalyst for low temperature shift (LTS) was prepared.

The prepared catalyst was subjected to the HTS reaction of the iron-chromium catalyst at 350 ° C. and the LTS reaction of the Cu-Zn / Al ₂ O ₃ catalyst at 225 ° C. using a fixed bed reactor at a space velocity of 1,000 / hr. . The reaction gas conditions were LDG simulated gas, in which volume%, H ₂ O was injected into CO.H ₂ O = 3 into 17.8% CO ₂ , 64.4% CO, 2% H ₂ and 15.8% N ₂ . Water gas conversion activity results are shown in Table 3.

Furthermore, CO ₂ was removed from the water gas-converted exhaust gas using an activated carbon adsorbent. Table 3 shows the composition of the gas after CO ₂ removal.

[Table 3]

Furtherance After water gas shift reaction (vol%) After CO ₂ removal (vol%) CO ₂ 56 - CO > 0.1% - H ₂ 33% 75 N ₂ 11% 25

Table 3 shows the composition of the dry gas after the water gas conversion catalyst reaction, it can be confirmed that the volume ratio of H ₂ / N ₂ is ~ 3 which is a suitable raw material composition for synthesizing ammonia. Therefore, in order to adjust to have such a ratio, a separate nitrogen supply step, which is conventionally required, is unnecessary, and the process can be simplified.

In addition, ammonia can be prepared using the Haber-Bosch method, which is a commonly used method using source gas, and high concentration carbon dioxide (> 50%) obtained in this process can be easily separated.

It can be seen that urea can be prepared using the separated carbon dioxide and ammonia prepared in this process.

1 is a conceptual diagram of ammonia manufacturing process according to the prior art.

2 is a conceptual diagram of ammonia and urea manufacturing process according to the present invention.

Claims (6)

An aqueous gas conversion step of producing hydrogen and carbon dioxide by catalyzing carbon monoxide and supplied water in the converter gas by supplying water to the converter gas as a steelmaking process gas; A carbon dioxide separation step of separating and removing the produced carbon dioxide; A methanation step of removing the carbon monoxide and carbon dioxide by reacting the carbon dioxide of carbon monoxide remaining in the converter gas with the hydrogen to methanate; And Ammonia from converter gas comprising ammonia production step by Haber-Bosch process using Fe-based catalyst at 150-250atm / 300-550 ° C as raw material using hydrogen obtained from water gas conversion reaction of carbon monoxide and converter gas How to prepare. The method of claim 1, wherein the carbon dioxide separation step removes impurities in carbon dioxide and purifies the carbon dioxide having a purity of 99.5% or more. The method of claim 1, wherein the catalyst used in the water gas shifting step is a catalyst of Fe or Cu-containing compounds. The catalyst of claim 4, wherein the catalyst is Fe ₃ O, Cr ₂ O ₃ / Fe ₃ O ₄ , CuO / Cr ₂ O ₃ / Fe ₃ O ₄ , Cu / ZnO, Cu / ZrO ₂ , Cu / ZnO / Al ₂ A process for producing ammonia from a converter gas which is at least one compound selected from O ₃ . The method of claim 1, wherein the carbon dioxide separation step separates carbon dioxide by chemical absorption using ethanolamine aqueous solution or pressure swing adsorption (PSA) adsorption using a solid adsorbent. A method for producing urea by reacting ammonia produced by the method of any one of claims 1 to 5 with carbon dioxide obtained from the carbon dioxide separation step.

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