Ammonia recovery device and method

Abstract

The present invention provides an ammonia recovery device comprising: a first ammonia purification column for separating impurity gas from a mixed gas containing ammonia; a second ammonia purification column for separating a first residual impurity gas from the mixed gas that has passed through the first ammonia purification column; and a third ammonia purification column for separating a second residual impurity gas from the mixed gas that has passed through the second ammonia purification column.

Description

Ammonia recovery device and method

[0001] The present invention relates to a device and method for recovering ammonia from a mixed gas.

[0002] Ammonia, a compound of nitrogen and hydrogen with the chemical formula NH3, can be used in various technologies, including as a NOx reducing agent in SCR (selective catalytic reduction). SCR technology removes NOx generated from combustion facilities such as power plants, which are stationary sources, or from mobile sources such as automobiles, using urea solution as the reducing agent. Urea solution is considered the same technology because it decomposes at high temperatures into ammonia, which then reacts with NOx.

[0003] As environmental issues increase, the number of SCR facilities for NOx removal is increasing, and ammonia usage is also increasing accordingly. Therefore, technology for supplying large quantities of high-purity ammonia is urgently needed.

[0004] Typically, ammonia synthesis and separation technology involves synthesizing H2 from natural gas, reacting it with nitrogen separated through an air separation unit (ASU) to synthesize ammonia (NH3), and then separating the synthesized ammonia. In most cases, the separation is achieved by exploiting the differences in boiling points between ammonia, hydrogen, and nitrogen.

[0005] Meanwhile, when separating ammonia and impurity gases such as H2S, CO2, H2O, and HCN by utilizing the difference in boiling points, the mixed gas containing ammonia must be cooled or heated to an appropriate temperature, and in particular, there is a problem that excessive energy is required for cooling.

[0006] Accordingly, there is a need to develop technology that can reduce energy consumption during the cooling process and further improve ammonia recovery efficiency.

[0007] According to one embodiment of the present invention, a device or method for removing impurity gases other than ammonia from a mixed gas containing ammonia and recovering high-purity ammonia can be provided.

[0008] According to another embodiment of the present invention, a device or method for recovering ammonia can be provided, which reduces energy consumed in the cooling process by cooling a mixed gas containing ammonia through heat exchange.

[0009] According to one embodiment of the present invention, an ammonia recovery device is provided, comprising: a first ammonia purification tower for separating impurity gas from a mixed gas containing ammonia (hereinafter referred to as “mixed gas”); a second ammonia purification tower for separating a first residual impurity gas from the mixed gas passing through the first ammonia purification tower; and a third ammonia purification tower for separating a second residual impurity gas from the mixed gas passing through the second ammonia purification tower.

[0010] The above impurity gas is at least one selected from the group consisting of H2S, CO2, H2O and HCN,

[0011] The above first residual impurity gas is a gas having a lower boiling point than ammonia among the above impurity gases,

[0012] The second residual impurity gas may be a gas having a higher boiling point than ammonia among the impurity gases.

[0013] The second ammonia purification tower includes a heat exchanger; a heat exchange fluid compressor; a heat exchange fluid cooler; a pressure reducing valve; and a gas-liquid separator, and can cool the mixed gas through heat exchange with a heat exchange fluid circulating in the heat exchange fluid circuit.

[0014] The above heat exchange fluid may be ammonia.

[0015] The above first ammonia purification tower can separate impurity gas from the mixed gas at a temperature of 20 to 60°C and a pressure of 0 to 3 barg.

[0016] The second ammonia purification tower can separate the first residual impurity gas by cooling the mixed gas that has passed through the first ammonia purification tower to -60 to 0°C at a pressure of 1 to 20 barg.

[0017] The third ammonia purification tower can separate the second residual impurity gas by cooling the mixed gas that has passed through the second ammonia purification tower to -20 to 30°C at a pressure of 1 to 20 barg.

[0018] According to another embodiment of the present invention, an ammonia recovery method is provided, comprising: a step S1 of separating an impurity gas from a mixed gas containing ammonia; a step S2 of separating a first residual impurity gas from the mixed gas passing through the step S1; and a step S3 of separating a second residual impurity gas from the mixed gas passing through the step S2.

[0019] The above S2 step includes a heat exchange step of cooling the mixed gas through heat exchange with a heat exchange fluid,

[0020] The above heat exchange step

[0021] (i) a step of pressurizing a heat exchange fluid;

[0022] (ii) a step of cooling the pressurized heat exchange fluid;

[0023] (iii) a step of depressurizing the pressurized and cooled heat exchange fluid;

[0024] (iv) a step of separating the depressurized heat exchange fluid into gas and liquid, and

[0025] (v) It may include a step of heat-exchanging a liquid heat-exchange fluid among the above-mentioned gas-liquid separated heat-exchange fluids with ammonia.

[0026] The above step S1 may be a step of separating impurity gas from the mixed gas at a temperature of 20 to 60°C and a pressure of 0 to 3 barg.

[0027] The above step S2 may be a step of separating the first residual impurity gas by cooling the mixed gas that has passed through the above step S1 to -60 to 0°C at a pressure of 1 to 20 barg.

[0028] The above step S3 may be a step of separating the second residual impurity gas by cooling the mixed gas that has passed through the above step S2 to -20 to 30°C at a pressure of 1 to 20 barg.

[0029] According to the ammonia recovery device or method of the present invention, high-purity ammonia can be recovered from a mixed gas containing ammonia.

[0030] In addition, according to the ammonia recovery device or method of the present invention, the energy consumed in the cooling process during the process of separating ammonia and impurity gases such as H2S, CO2, and H2O from a mixed gas containing ammonia can be reduced, and thus ammonia can be recovered more economically.

[0031] Figure 1 is a schematic diagram of an ammonia recovery device according to one embodiment of the present invention.

[0032] Figure 2 is a schematic diagram of an ammonia recovery device according to another embodiment of the present invention.

[0033] Figure 3 schematically illustrates the flow of fluid streams ([A] to [K]) in the ammonia recovery device of Figure 1.

[0034] Figure 4 schematically illustrates the flow of fluid streams ([A] to [K]) and heat exchange streams ([R-01] to [R-09]) in the ammonia recovery device of Figure 2.

[0035] Figure 5 is a flowchart of an ammonia recovery method according to one embodiment of the present invention.

[0036] 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 in various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0037] In addition, the embodiments of the present invention are provided to more completely explain the present invention to a person having average knowledge in the relevant technical field.

[0038] In describing the embodiments of the present invention, if a detailed description of a known technology related to the present invention is judged to unnecessarily obscure the gist of the present invention, such detailed description will be omitted. In addition, the terms described below are terms defined in consideration of their functions in the present invention, and these may vary depending on the intention or custom of the user or operator. Therefore, the definitions should be made based on the contents throughout this specification. The terminology used in the detailed description is only for the purpose of describing the embodiments of the present invention and should in no way be limiting. Unless clearly defined otherwise, expressions in the singular form include plural meanings.

[0039] Below, the present invention will be described in detail through each embodiment or example of the present invention. It should be noted that each embodiment or example described in this specification is not limited to a single embodiment or example, but may be combined with other embodiments or examples. Therefore, the citation of a claim in the patent claims is only an example of an embodiment, and the technical concept of the present invention should not be interpreted solely as a combination with the cited claim, and combinations with various claims also fall within the scope of the technical concept of the present invention.

[0040] Hereinafter, an ammonia recovery device according to one embodiment of the present invention will be described in more detail with reference to FIGS. 1 and 3.

[0041] According to one embodiment of the present invention, an ammonia recovery device is provided, including a first ammonia purification tower for separating impurity gas from a mixed gas containing ammonia (hereinafter referred to as a mixed gas); a second ammonia purification tower for separating a first residual impurity gas from the mixed gas passing through the first ammonia purification tower; and a third ammonia purification tower for separating a second residual impurity gas from the mixed gas passing through the second ammonia purification tower.

[0042] The above impurity gas may be at least one selected from the group consisting of H2S, CO2, H2O, and HCN. In addition, the first residual impurity gas may be a gas having a boiling point lower than ammonia among the impurity gases. The second residual impurity gas may be a gas having a boiling point higher than ammonia among the impurity gases.

[0043] The above mixed gas may be a byproduct gas generated during the steelmaking process, and more specifically, process gas generated at a coal plant may be used, but is not limited thereto. The above-mentioned coal plant refers to a place where a process of producing coke by carbonizing coal is performed.

[0044] Since the above mixed gas may be at a high temperature, the ammonia recovery device according to one embodiment of the present invention may include a first mixed gas cooler (1).

[0045] The above first mixed gas cooler (1) can control the mixed gas temperature to 20 to 60°C, more specifically, 30 to 50°C. This is because the temperature at which the removal of impurity gases (H2S, CO2, H2O, and HCN) by gas-liquid separation in the first ammonia purification tower (2) occurs smoothly is 60°C or lower.

[0046] The first ammonia purification tower (2) can remove impurity gases through gas-liquid separation. More specifically, the first ammonia purification tower (2) can include a gas-liquid separation drum, also called a knockout drum, as a gas-liquid separator. Therefore, when a mixed gas consisting of a gas and liquid mixture is supplied, the liquid containing ammonia is separated to the bottom of the gas-liquid separation drum, and the gas containing impurity gases is separated to the top of the gas-liquid separation drum, thereby removing the impurity gases.

[0047] The above first ammonia purification tower (2) can separate impurity gas from a mixed gas containing ammonia at a temperature of 20 to 60°C, more specifically, 30 to 50°C. This is because, as described above, the removal of impurity gas through gas-liquid separation in the first ammonia purification tower (2) is performed at an operating temperature of 60°C or lower.

[0048] In addition, the first ammonia purification tower (2) can separate impurity gases from a mixed gas containing ammonia at a pressure of 0 to 3 barg, more specifically, 0 to 1 barg. A condition of less than 0 barg means that the pressure must be reduced to below atmospheric pressure, which is an unnecessary consumption of energy, and if the pressure exceeds 3 barg, excessive energy consumption for pressurization may occur.

[0049] Meanwhile, as will be described later, in order to separate and remove the first residual impurity gas having a boiling point lower than ammonia, such as carbon dioxide and hydrogen sulfide, from the mixed gas in the second ammonia purification tower (5), the mixed gas must be cooled, and at this time, excessive energy may be consumed.

[0050] Accordingly, an ammonia recovery device according to one embodiment of the present invention may include a compression pump (3) for pressurizing a mixed gas. The compression pump (3) pressurizes the mixed gas to raise the boiling point of each gas contained in the mixed gas, thereby enabling condensation of the gases at a higher temperature, thereby preventing excessive energy consumption for cooling the mixed gas.

[0051] The above compression pump (3) can pressurize the mixed gas to 1 to 20 barg, and more specifically, to 5 to 10 barg.

[0052] If the pressure of the mixed gas is less than 1 barg, the boiling points of each gas contained in the mixed gas are not sufficiently high, and thus excessive energy may be consumed for cooling the mixed gas in the second ammonia purification tower (5) described later. If the pressure of the mixed gas exceeds 20 barg, excessive energy may be consumed for pressurization.

[0053] Meanwhile, since the temperature within the mixed gas increases when the mixed gas is pressurized by the compression pump (3) (adiabatic compression), the ammonia recovery device according to one embodiment of the present invention may include a second mixed gas cooler (4) for cooling the pressurized mixed gas.

[0054] The above second mixed gas cooler (4) can control the temperature of the mixed gas to 20 to 40°C, more specifically, 20 to 30°C. This is to prevent the temperature of the mixed gas from becoming excessively high, thereby enabling the separation and removal of the first residual impurity gas using the distillation method performed in the second ammonia purification tower (5) to be smoothly performed.

[0055] An ammonia recovery device according to one embodiment of the present invention may include a second ammonia purification tower (5) for separating a first residual impurity gas having a boiling point lower than ammonia from a mixed gas passing through the first ammonia purification tower.

[0056] The above first residual impurity gas is a gas having a boiling point lower than ammonia among the impurity gases, and may be, for example, at least one selected from carbon dioxide and hydrogen sulfide.

[0057] The above second ammonia purification tower (5) can separate and remove the first residual impurity gas from the mixed gas that has passed through the above first ammonia purification tower (2) using a distillation method.

[0058] The above second ammonia purification tower (5) may be equipped with a cooler at the top and a reboiler at the bottom, and may be loaded with a filler inside.

[0059] The filler may be a filler composed of at least one of ceramic, carbon, and carbon steel. The shape of the filler may be selected from the group consisting of, but is not limited to, a sphere, a cylinder, a pallring, a saddle, and a random packing.

[0060] In the above second ammonia purification tower (5), a gas-liquid equilibrium of ammonia is formed in each stage formed by the filling material, and at this time, ammonia gas and the first residual impurity gas can be separated from each other due to differences in boiling point and volatility.

[0061] In the second ammonia purification tower (5), the mixed gas that has passed through the first ammonia purification tower (2) can be cooled to -60 to 0°C by the cooler of the second ammonia purification tower, more specifically, to -40 to -10°C, and even more specifically, to -30 to -10°C.

[0062] If the temperature cooled by the cooler of the second ammonia purification tower is below -60°C, the cooling process may consume significant energy, increasing process costs. Conversely, if the temperature exceeds 0°C, the ammonia may not be sufficiently cooled, resulting in a decrease in the amount of ammonia recovered from the bottom.

[0063] Additionally, the pressure inside the second ammonia purification tower (10) may be 1 to 20 barg, and more specifically, 5 to 10 barg.

[0064] If the pressure inside the second ammonia purification tower (5) is less than 1 barg, ammonia may be discharged and lost to the top. Conversely, if it exceeds 20 barg, excessive energy input may be required for reboiling at the bottom of the distillation tower, which may result in poor economic efficiency.

[0065] The above mixed gas can be reheated by the reboiler of the second ammonia purification tower.

[0066] In the process where the above mixed gas is cooled by the cooler of the second ammonia purification tower and then heated again by the reboiler of the second ammonia purification tower, ammonia with a relatively high boiling point is recovered from the bottom of the second ammonia purification tower (5), and the first residual impurity gas can be separated and removed in a gaseous state from the top of the second ammonia purification tower (5).

[0067] The mixed gas recovered from the second ammonia purification tower (5) can be fed into the third ammonia purification tower (7). The third ammonia purification tower (7) can separate and remove the second residual impurity gas having a boiling point higher than ammonia from the mixed gas.

[0068] The second residual impurity gas may be a gas having a boiling point higher than ammonia among the impurity gases, and may be, for example, at least one selected from water (H2O) and hydrogen cyanide (HCN).

[0069] The above third ammonia purification tower (7) is not particularly limited as long as it can separate the second residual impurity gas having a higher boiling point than ammonia, but for example, the second residual impurity gas can be separated and removed using distillation.

[0070] The above third ammonia purification tower (7) may be equipped with a cooler at the top and a reboiler at the bottom.

[0071] The cooler of the third ammonia purification tower can serve to cool the mixed gas fed into the third ammonia purification tower (7). The mixed gas can be cooled to -20 to 30°C by the cooler of the third ammonia purification tower, more specifically to -5 to 30°C, and even more specifically to 0 to 30°C.

[0072] If the temperature cooled by the cooler of the third ammonia purification tower is below -20℃, the cooling process may consume a lot of energy, which may increase the process cost, and the supercooling of water may cause ice to form, clogging the pipes.

[0073] Conversely, if the temperature exceeds 30°C, the temperature may not be sufficiently cooled to allow separation of water and ammonia, and thus the separation and removal of the second residual impurity gas at the bottom may not be sufficient, resulting in a problem of not being able to recover ammonia of sufficient purity.

[0074] The pressure inside the third ammonia purification tower (7) may be 1 to 20 barg, and more specifically, 5 to 10 barg.

[0075] If the pressure inside the third ammonia purification tower (7) is less than 1 barg, a problem may arise where ammonia is discharged and lost to the top. Conversely, if it exceeds 20 barg, excessive energy input may be required for reboiling at the bottom of the distillation tower, which may result in poor economic efficiency.

[0076] Meanwhile, ammonia purification performed by distillation has the problem of requiring energy for cooling the gas as described above, and in particular, in the second ammonia purification tower (5), there is the problem of requiring excessive energy as the temperature at which the mixed gas is cooled is the lowest.

[0077] Accordingly, the ammonia recovery device according to one embodiment of the present invention may include a heat exchange fluid circuit instead of or in addition to the cooler of the second ammonia purification tower. The heat exchange fluid circuit may include a heat exchanger (8); a heat exchange fluid compressor (9); a heat exchange fluid cooler (10); a pressure reducing valve (11); and a gas-liquid separator (12), and a heat exchange fluid may be circulated therein.

[0078] Hereinafter, an ammonia recovery device according to another embodiment of the present invention will be described in more detail with reference to FIGS. 2 and 4.

[0079] The above heat exchanger (8) is located at the top of the second ammonia purification tower (5), and can cool the mixed gas through heat exchange with a heat exchange fluid by replacing or supplementing the role of the cooler of the second ammonia purification tower.

[0080] The above heat exchange fluid compressor (9) can increase the pressure of the heat exchange fluid to 3 to 20 barg, and more specifically, to 5 to 10 barg.

[0081] If the pressure of the heat exchange fluid is less than 3 barg, the temperature of the heat exchange fluid may not be sufficiently lowered when pressure is reduced (adiabatic expansion) in the pressure reducing valve (11) described later. If the pressure of the heat exchange fluid exceeds 20 barg, excessive energy may be consumed to pressurize the heat exchange fluid.

[0082] The above heat exchange fluid cooler (10) can control the temperature of the heat exchange fluid that has risen during the pressurization process to 30 to 60°C, more specifically, 40 to 50°C. This is to control the temperature of the heat exchange fluid so that it can be sufficiently lowered when pressure reduction (adiabatic expansion) occurs in the pressure reducing valve (11) described later.

[0083] The above heat exchange fluid compressor (9) and heat exchange fluid cooler (10) can be provided independently in multiple numbers.

[0084] The above pressure reducing valve (11) can cool the heat exchange fluid by reducing the pressure of the pressurized heat exchange fluid to allow adiabatic expansion.

[0085] Meanwhile, when the pressure of the heat exchange fluid is reduced in the pressure reducing valve (11), some of the heat exchange fluid may vaporize as the boiling point of the heat exchange fluid decreases. Since the gaseous heat exchange fluid has low thermal conductivity and thus poor heat exchange efficiency, the heat exchange fluid circuit can separate the gaseous heat exchange fluid and the liquid heat exchange fluid through the gas-liquid separator (12). Accordingly, only the liquid heat exchange fluid can be supplied to the heat exchanger (8).

[0086] The liquid heat exchange fluid supplied to the above heat exchanger (8) can be vaporized during the process of performing heat exchange with the mixed gas and then combined again with the gaseous heat exchange fluid (Fig. 2).

[0087] The heat exchange fluid is not particularly limited, but at least one selected from the group consisting of water and ammonia may be used. For example, a portion of the ammonia recovered by the ammonia recovery device and method according to the present invention may be used as the heat exchange fluid.

[0088] When ammonia is used as the heat exchange fluid, the flow rate of the heat exchange fluid circulating through the heat exchange circuit may be 5,000 to 12,000 kg / h, more specifically, 6,000 to 10,000 kg / h. When the flow rate of the heat exchange fluid circulating through the heat exchange circuit is within the above range, the mixed gas in the second ammonia purification tower can be cooled using only the vaporization heat of the heat exchange fluid, which can be efficient.

[0089] Meanwhile, the heat exchange fluid circuit may further include a heat exchange fluid supply pump (13) to supplement heat exchange fluid lost during process operation.

[0090] An ammonia recovery device according to one embodiment of the present invention can recover ammonia more economically by reducing excessive energy consumed in cooling the mixed gas by including the heat exchange fluid circuit.

[0091] According to another embodiment of the present invention, an ammonia recovery method is provided, comprising: a step S1 of separating an impurity gas from a mixed gas containing ammonia; a step S2 of separating a first residual impurity gas from the mixed gas passing through the step S1; and a step S3 of separating a second residual impurity gas from the mixed gas passing through the step S2.

[0092] Hereinafter, an ammonia recovery method according to another embodiment of the present invention will be described in more detail with reference to FIG. 5.

[0093] The above step S1 can separate impurity gas from a mixed gas containing ammonia at a temperature of 20 to 60°C and a pressure of 0 to 3 barg. The above step S1 can separate impurity gas from the mixed gas by gas-liquid separation. Since the temperature and pressure conditions under which the above step S1 is performed have been described above with respect to the first ammonia purification tower (2) among the ammonia recovery devices according to one embodiment of the present invention, a description thereof will be omitted below.

[0094] The above S2 step can separate the first residual impurity gas from the mixed gas that passed through the S1 step by cooling the mixed gas that passed through the S1 step to -60 to 0°C, more specifically to -40 to -10°C, and even more specifically to -30 to -10°C at a pressure of 1 to 20 barg. Since the temperature and pressure conditions under which the S2 step is performed have been described above with respect to the second ammonia purification tower (5) of the ammonia recovery device according to one embodiment of the present invention, a description thereof will be omitted below.

[0095] The above step S2 may further include a step of cooling the mixed gas that has passed through the above step S1; a step of separating and removing the first residual impurity gas in a gaseous state; and a step of re-heating the gas from which the first residual impurity gas has been removed. Each of the above steps may be performed intermittently or continuously.

[0096] The above S3 step can separate the second residual impurity gas from the mixed gas that passed through the S2 step by cooling the mixed gas that passed through the S2 step to -20 to 30°C, more specifically -5 to 30°C, and even more specifically 0 to 30°C at a pressure of 1 to 20 barg. Since the temperature and pressure conditions under which the S3 step is performed have been described above with respect to the third ammonia purification tower (7) of the ammonia recovery device according to one embodiment of the present invention, a description thereof will be omitted below.

[0097] The above step S3 may further include a step of cooling the mixed gas that has passed through the above step S2; a step of separating and removing the second residual impurity gas in a liquid state; and a step of re-heating the gas from which the second residual impurity gas has been removed. Each of the above steps may be performed intermittently or continuously.

[0098] Meanwhile, the S2 step may include a heat exchange step of cooling the mixed gas through heat exchange with a heat exchange fluid.

[0099] The above heat exchange steps are:

[0100] (i) a step of pressurizing a heat exchange fluid;

[0101] (ii) a step of cooling the pressurized heat exchange fluid;

[0102] (iii) a step of depressurizing the pressurized and cooled heat exchange fluid;

[0103] (iv) a step of separating the depressurized heat exchange fluid into gas and liquid, and

[0104] (v) It may include a step of heat-exchanging a liquid heat-exchange fluid among the above-mentioned gas-liquid separated heat-exchange fluids with ammonia.

[0105] The ammonia recovery method according to one embodiment of the present invention includes the heat exchange step, thereby reducing excessive energy consumed in cooling the mixed gas, thereby enabling ammonia recovery more economically.

[0106] Hereinafter, the present invention will be described in detail through examples. However, it should be noted that the examples described below are intended only to illustrate and concretize the present invention and are not intended to limit the scope of the invention. This is because the scope of the invention is determined by the matters set forth in the patent claims and matters reasonably inferred therefrom.

[0107] Example 1

[0108] A mixed gas containing ammonia was supplied to an ammonia recovery device configured as shown in Fig. 1, and ammonia was recovered from the mixed gas.

[0109] At this time, the mixed gas was pressurized to 10 barg by the compression pump (3), so that the second ammonia purification tower (5) and the third ammonia purification tower (7) performed ammonia purification, i.e., separation of impurity gas, under the 10 barg condition.

[0110] Tables 1 and 2 below show the temperature, pressure, and flow rate of each fluid stream, as well as the components and contents of gases identified in each fluid stream. Streams A to K in Tables 1 and 2 correspond to [A] to [K] in Fig. 3, respectively.

[0111] Fluid Stream ABC DEF Temperature (℃) 85.0 30.0 30.0 30.0 37.0 30.0 Pressure (barg) 0.2 0.2 0.2 0.2 10.0 10.0 Flow (kmol / h) 340.6 340.6 50.7 289.8 289.8 289.8 Composition (mol%) CO 2 0.1 387 8 10.1 387 8 10.3 31 16 0.1 04 76 30.1 04 76 30.1 04 76 30.1 04 76 3 NH 3 0.2 60 0 170.2 60 0 170.1 52 26 7 0.2 78 8 78 0.2 78 8 78 H 2 S 0.1238980.1238980.4369560.0690980.0690980.069098HCN0.0269460.0269460.059240 0.0212930.0212930.021293H2O0.4503590.4503590.0184220.5259690.5259690.525969

[0112] Fluid Stream GHIJK Temperature (℃) -12.4 10 4.2 4 0.0 2 8.3 16 4.5 Pressure (barg) 10.0 10.0 10.0 10.0 10.0 Flow Rate (kmol / h)56.0233.8233.874.6159.3Component(mol%)CO20.5422390.0000000.0000000.0000000.000000NH30.1001550.3216770.3216770.9999730.004061H2S0.3576060.0000080.0000080.0000250.000000HCN0.0000000.0263910.0263910.0000010.038749H2O0.0000000.6519230.6519230.0000000.957191

[0113] Referring to FIG. 1, FIG. 3, Table 1 and Table 2, it was confirmed that some CO2, H2S, HCN and H2O were separated from the mixed gas in the first ammonia purification tower (2).

[0114] Additionally, it was confirmed that the first residual impurity gas (CO2 and H2S) having a relatively low boiling point compared to ammonia was separated in the second ammonia purification tower (5).

[0115] Additionally, it was confirmed that the second residual impurity gas (HCN and H2O) having a relatively high boiling point compared to ammonia was separated in the third ammonia purification tower (7).

[0116] In addition, as a result of performing ammonia purification by pressurizing the mixed gas to 10 barg, it was confirmed that the cooling temperature in the second ammonia purification tower (5) required to perform ammonia purification was -12.4°C and the cooling temperature in the third ammonia purification tower (7) was 28.3°C, which is close to room temperature.

[0117] Meanwhile, as a result of performing ammonia purification by pressurizing the mixed gas to 10 barg, it was confirmed that the purity of the purified ammonia was 99.9973 mol%.

[0118] Example 2

[0119] The second ammonia purification tower (5) and the third ammonia purification tower (7) were performed in the same manner as in Example 1, except that the pressure of the mixed gas pressurized by the compression pump (3) was changed to 5 barg, and ammonia purification was performed under 5 barg conditions.

[0120] Tables 3 and 4 below show the temperature, pressure, and flow rate of each fluid stream, as well as the components and contents of gases identified in each fluid stream. Streams A to K in Tables 3 and 4 correspond to [A] to [K] in Fig. 3, respectively.

[0121] Fluid Stream ABC DEF Temperature (℃) 85.0 30.0 30.0 30.0 36.9 30.0 Pressure (barg) 0.2 0.2 0.2 0.2 0.2 5.0 5.0 Flow (kmol / h) 340.6 340.6 50.7 289.8 289.8 289.8 Composition (mol%) CO 2 0.1 387 8 10.1 387 8 10.3 31 16 0.1 04 76 30.1 04 76 30.1 04 76 30.1 04 76 3 NH 3 0.2 60 0 170.2 60 0 170.1 52 26 7 0.2 78 8 78 0.2 78 8 78 H 2 S 0.1238980.1238980.4369560.0690980.0690980.069098HCN0.0269460.0269460.059240 0.0212930.0212930.021293H2O0.4503590.4503590.0184220.5259690.5259690.525969

[0122] Fluid Stream GHIJK Temperature (℃) -28.374.740.09.6134.9 Pressure (barg) 5.05.05.05.05.0 Flow Rate (kmol / h)56.0233.8233.874.6159.2Component(mol%)CO20.5421480.0000000.0000000.0000000.000000NH30.1002770.3216570.3216570.9999960.003980H2S0.3575740.0000010.0000010.0000040.000000HCN0.0000000.0263930.0263930.0000000.038752H2O0.0000000.6519490.6519490.0000000.957267

[0123] Referring to Table 3 and Table 4, as a result of performing ammonia purification by pressurizing the mixed gas to 5 barg, it was confirmed that the cooling temperature in the second ammonia purification tower (5) required to perform ammonia purification was -28.3°C and the cooling temperature in the third ammonia purification tower (7) was 9.6°C.

[0124] Meanwhile, as a result of performing ammonia purification by pressurizing the mixed gas to 5 barg, it was confirmed that the purity of the purified ammonia was 99.9996 mol%.

[0125] Example 3

[0126] The second ammonia purification tower (5) and the third ammonia purification tower (7) were performed in the same manner as in Example 1, except that the pressure of the mixed gas pressurized by the compression pump (3) was changed to 3 barg, and ammonia purification was performed under 3 barg conditions.

[0127] Tables 5 and 6 below show the temperature, pressure, and flow rate of each fluid stream, as well as the components and contents of gases identified in each fluid stream. Streams A to K in Tables 5 and 6 correspond to [A] to [K] in Fig. 3, respectively.

[0128] Fluid Stream ABC DEF Temperature (℃) 85.0 30.0 30.0 30.0 36.8 30.0 Pressure (barg) 0.2 0.2 0.2 0.2 0.2 3.0 3.0 Flow (kmol / h) 340.6 340.6 50.7 289.8 289.8 289.8 Composition (mol%) CO 2 0.1 387 8 10.1 387 8 10.3 31 60.1 04 76 30.1 04 76 30.1 04 76 30.1 04 76 3 NH 3 0.2 60 0 170.2 60 0 170.1 52 26 7 0.2 78 8 78 0.2 78 8 78 H 2 S 0.1238980.1238980.4369560.0690980.0690980.069098HCN0.0269460.0269460.059240 0.0212930.0212930.021293H2O0.4503590.4503590.0184220.5259690.5259690.525969

[0129] Fluid Stream GHIJK Temperature (℃) -37.757.340.0 -1.5116.5 Pressure (barg) 3.03.03.03.03.0 Flow Rate (kmol / h)56.0233.8233.874.6159.2Component(mol%)CO20.5421640.0000000.0000000.0000000.000000NH30.1002480.3216620.3216620.9999990.003983H2S0.3575880.0000000.000000.0000010.000000HCN0.0000000.0263920.0263920.0000000.038752H2O0.0000000.6519450.6519450.0000000.957264

[0130] Referring to Table 5 and Table 6, as a result of performing ammonia purification by pressurizing the mixed gas to 3 barg, it was confirmed that the cooling temperature in the second ammonia purification tower (5) required to perform ammonia purification was -37.7°C and the cooling temperature in the third ammonia purification tower (7) was -1.5°C.

[0131] Meanwhile, as a result of performing ammonia purification by pressurizing the mixed gas to 3 barg, it was confirmed that the purity of the purified ammonia was 99.9999 mol%.

[0132] Example 4

[0133] The second ammonia purification tower (5) and the third ammonia purification tower (7) were performed in the same manner as in Example 1, except that the pressure of the mixed gas pressurized by the compression pump (3) was changed to 1 barg, and ammonia purification was performed under 1 barg conditions.

[0134] Tables 7 and 8 below show the temperature, pressure, and flow rate of each fluid stream, as well as the components and contents of gases identified in each fluid stream. Streams A to K in Tables 7 and 8 correspond to [A] to [K] in Fig. 3, respectively.

[0135] Fluid Stream ABC DEF Temperature (℃) 85.0 30.0 30.0 30.0 36.8 30.0 Pressure (barg) 0.2 0.2 0.2 0.2 0.2 1.0 Flow (kmol / h) 340.6 340.6 50.7 289.8 289.8 289.8 Composition (mol%) CO 2 0.1 387 8 10.1 387 8 10.3 31 16 0.1 04 76 30.1 04 76 30.1 04 76 30.1 04 76 3 NH 3 0.2 60 0 170.2 60 0 170.1 52 26 7 0.2 78 8 78 0.2 78 8 78 H 2 S 0.1238980.1238980.4369560.0690980.0690980.069098HCN0.0269460.0269460.059240 0.0212930.0212930.021293H2O0.4503590.4503590.0184220.5259690.5259690.525969

[0136] Fluid Stream GHIJK Temperature (℃) -51.931.340.0 -18.487.7 Pressure (barg) 1.01.01.01.01.0 Flow Rate (kmol / h)56.0233.8233.874.6159.2Component(mol%)CO20.5421760.0000000.0000000.0000000.000000NH30.1002270.3216660.3216661.0000000.003991H2S0.3575970.0000000.0000000.000000.000000HCN0.0000000.0263920.0263920.0000000.038752H2O0.0000000.6519410.6519410.0000000.957257

[0137] Referring to Table 7 and Table 8, as a result of performing ammonia purification by pressurizing the mixed gas to 1 barg, it was confirmed that the cooling temperature in the second ammonia purification tower (5) required to perform ammonia purification was -51.9°C and the cooling temperature in the third ammonia purification tower (7) was -18.4°C.

[0138] Meanwhile, as a result of performing ammonia purification by pressurizing the mixed gas to 1 barg, it was confirmed that the purity of the purified ammonia was 100 mol%.

[0139] Example 5

[0140] The same procedure as in Example 1 was performed except that the cooler of the second ammonia purification tower was replaced with a heat exchanger (8); a heat exchange fluid compressor (9); a heat exchange fluid cooler (10); a pressure reducing valve (11); and a gas-liquid separator (12) as shown in Fig. 2.

[0141] Accordingly, it was confirmed that the fluid streams [A] to [K] had the same temperature, pressure, flow rate, gas composition and content as in Tables 1 and 2 above (see Example 1 above).

[0142] Meanwhile, the heat exchange fluid compressor (9) and the heat exchange fluid cooler (10) were configured to be connected in series in pairs, and ammonia was used as the heat exchange fluid circulating in the heat exchange fluid circuit.

[0143] Tables 9 and 10 below show, in order, the vapor partial pressure, temperature, pressure, and flow rate of the heat exchange stream when the heat exchange efficiency is 90% and 50% in Example 5, respectively. Heat exchange streams R-01 to R-09 in Tables 9 and 10 correspond to [R-01] to [R-09] in Fig. 4, respectively.

[0144] Heat Exchange Stream R-01R-02R-03R-04R-05R-06R-07R-08R-09 Vapor Fraction 1.01.01.01.00.00.31.00.01.0 Temperature (℃) -33.0133.045.0176.545.1-33.0-33.0-33.0-33.0 Pressure (barg) 0.04.64.616.716.70.00.00.00.0 Flow Rate (kmol / h) 324.7324.7324.7324.7324.788.0236.7236.7 Flow Rate (kg / h)5530.05530.05530.05530.05530.05530.01498.84031.24031.2

[0145] Heat Exchange Stream R-01 R-02 R-03 R-04 R-05 R-06 R-07 R-08 R-09 Vapor Fraction 1.0 1.0 1.0 1.0 1.0 0.0 0.3 1.0 0.0 1.0 Temperature (℃) -33.0 1.33.0 4.5 1.76.5 4.5 1.33.0 3.0 3.0 3.0 3.0 Pressure (barg) 0.04.6 4.6 1.6 1.6 7.0 0.00.00.00.0 Flow Rate (kmol / h) 5.84.45 8.45 8.45 8.45 8.45 8.41 5.8 4.26 0.426 0.0 Flow Rate (kg / h)9953.09953.09953.09953.09953.09953.02697.67255.47255.4

[0146] Referring to Tables 9 and 10, it was confirmed that the ammonia recovery device according to one embodiment of the present invention can cool the mixed gas passing through the ammonia recovery device through heat exchange with ammonia. In addition, it was confirmed that under the condition that the mixed gas is pressurized to a pressure of 10 barg, when the heat exchange fluid (ammonia) is circulated at a flow rate of 5530 kg / h to 9953 kg / h, the mixed gas can be cooled only by the vaporization heat generated during the phase change process without a change in the temperature of the heat exchange fluid.

[0147] Meanwhile, when the mixed gas is cooled through heat exchange in the second ammonia purification tower as in Example 5 (mixed gas pressure: 10 barg), the sum of the power consumed to drive the heat exchange fluid compressor (9) was measured to be 0.9616 MW (under the condition of 90% heat exchange efficiency) to 1.7308 MW (under the condition of 50% heat exchange efficiency). Meanwhile, under the same conditions, when direct cooling is performed using the cooler of the second ammonia purification tower, a power of 1.9 MW (assuming an energy efficiency ratio (EER) of 2.5) is required when using a general industrial cooler.

[0148] Therefore, it was confirmed that when the mixed gas is cooled through heat exchange under the condition of pressurizing the above mixed gas to a pressure of 10 barg, the power consumption is reduced by 8.9% to 49.4% compared to when the mixed gas is cooled directly using a cooler.

[0149] Example 6

[0150] The second ammonia purification tower (5) and the third ammonia purification tower (7) were performed in the same manner as in Example 5, except that the pressure of the mixed gas pressurized by the compression pump (3) was changed to 5 barg, and ammonia purification was performed under 5 barg conditions.

[0151] Tables 11 and 12 below show, in order, the vapor partial pressure, temperature, pressure, and flow rate of the heat exchange stream when the heat exchange efficiency is 90% and 50% in Example 6, respectively. Heat exchange streams R-01 to R-09 in Tables 11 and 12 correspond to [R-01] to [R-09] in Fig. 4, respectively.

[0152] Heat Exchange Stream R-01 R-02 R-03 R-04 R-05 R-06 R-07 R-08 R-09 Vapor Fraction 1.0 1.0 1.0 1.0 1.0 0.0 0.3 1.0 0.0 1.0 Temperature (℃) -33.0 1.3 3.0 4.5 1.7 6.5 4.5 1.3 3.0 3.0 3.0 3.0 3.0 3.0 Pressure (barg) 0.0 4.6 4.6 1.6 1.6 7.0 0.0 0.0 0.0 Flow Rate (kmol / h) 3.5 0.4 3.5 0.4 3.5 0.4 3.5 0.4 3.5 0.4 9.5 0.2 5.5 4.2 5.4 Flow Rate (kg / h)5967.05967.05967.05967.05967.05967.01617.34349.74349.7

[0153] Heat Exchange Stream R-01R-02R-03R-04R-05R-06R-07R-08R-09 Vapor Fraction 1.01.01.01.00.00.31.00.01.0 Temperature (℃) -33.0133.045.0176.545.1-33.0-33.0-33.0-33.0 Pressure (barg) 0.04.64.616.716.70.00.00.00.0 Flow Rate (kmol / h) 630.7630.7630.7630.7630.7170.9459.8459.8 Flow Rate (kg / h)10741.010741.010741.010741.010741.010741.02911.27829.87829.8

[0154] Referring to Tables 11 and 12, it was confirmed that under the condition that the mixed gas was pressurized to a pressure of 5 barg, when the heat exchange fluid (ammonia) was circulated at a flow rate of 5967 kg / h to 10741 kg / h, the mixed gas could be cooled only by the heat of vaporization generated during the phase change process without a change in the temperature of the heat exchange fluid.

[0155] Meanwhile, when cooling the mixed gas through heat exchange in the second ammonia purification tower as in Example 6 (mixed gas pressure: 5 barg), the sum of the power consumed to drive the heat exchange fluid compressor (9) was measured to be 1.0377 MW (under the condition of 90% heat exchange efficiency) to 1.8674 MW (under the condition of 50% heat exchange efficiency). Meanwhile, under the same conditions, when direct cooling is performed using the cooler of the second ammonia purification tower, power of 2.1 MW (assuming an energy efficiency ratio (EER) of 2.5) is required when using a general industrial cooler.

[0156] Therefore, it was confirmed that when the mixed gas is cooled through heat exchange under the condition of pressurizing the above mixed gas to a pressure of 5 barg, the power consumption is reduced by 17.6% to 54.2% compared to when the mixed gas is cooled directly using a cooler.

[0157] [Explanation of symbols]

[0158] 1: First mixed gas cooler

[0159] 2: 1st ammonia purification tower

[0160] 3: Compression pump

[0161] 4: Second mixed gas cooler

[0162] 5: Second ammonia purification tower

[0163] 6: Third mixed gas cooler

[0164] 7: Third ammonia purification tower

[0165] 8: Heat exchanger

[0166] 9: Heat exchange fluid compressor

[0167] 10: Heat exchange fluid cooler

[0168] 11: Pressure relief valve

[0169] 12: Gas-liquid separator

[0170] 13: Heat exchange fluid supply pump

[0171] C: Cooler

[0172] H: Reboiler

Claims

1. A first ammonia purification tower for separating impurity gas from a mixed gas containing ammonia; A second ammonia purification tower for separating the first residual impurity gas from the mixed gas passing through the first ammonia purification tower; and It includes a third ammonia purification tower that separates the second residual impurity gas from the mixed gas that has passed through the second ammonia purification tower. The above impurity gas is at least one selected from the group consisting of H2S, CO2, H2O and HCN, The above first residual impurity gas is a gas having a lower boiling point than ammonia among the above impurity gases, An ammonia recovery device, wherein the second residual impurity gas is a gas having a higher boiling point than ammonia among the impurity gases.

2. In paragraph 1, The second ammonia purification tower includes a heat exchanger; a heat exchange fluid compressor; a heat exchange fluid cooler; a pressure reducing valve; and a gas-liquid separator. An ammonia recovery device that cools the mixed gas through heat exchange with a heat exchange fluid circulating in the above heat exchange fluid circuit.

3. In paragraph 2, An ammonia recovery device wherein the above heat exchange fluid is ammonia.

4. In paragraph 1, The above first ammonia purification tower is an ammonia recovery device that separates impurity gas from the mixed gas at a temperature of 20 to 60°C and a pressure of 0 to 3 barg.

5. In paragraph 1, The second ammonia purification tower is an ammonia recovery device that separates the first residual impurity gas by cooling the mixed gas that has passed through the first ammonia purification tower to -60 to 0°C at a pressure of 1 to 20 barg.

6. In paragraph 1, The third ammonia purification tower is an ammonia recovery device that separates the second residual impurity gas by cooling the mixed gas that has passed through the second ammonia purification tower to -20 to 30°C at a pressure of 1 to 20 barg.

7. Step S1 for separating impurity gas from a mixed gas containing ammonia; Step S2 for separating the first residual impurity gas from the mixed gas that has passed through the above step S1, and It includes a step S3 for separating a second residual impurity gas from the mixed gas that has passed through the step S2. The above impurity gas is at least one selected from the group consisting of H2S, CO2, H2O and HCN, The above first residual impurity gas is a gas having a lower boiling point than ammonia among the above impurity gases, An ammonia recovery method, wherein the second residual impurity gas is a gas having a higher boiling point than ammonia among the impurity gases.

8. In paragraph 7, The above S2 step includes a heat exchange step of cooling the mixed gas through heat exchange with a heat exchange fluid, The above heat exchange step (i) a step of pressurizing a heat exchange fluid; (ii) a step of cooling the pressurized heat exchange fluid; (iii) a step of depressurizing the pressurized and cooled heat exchange fluid; (iv) a step of separating the depressurized heat exchange fluid into gas and liquid; and (v) A method for recovering ammonia, comprising a step of heat-exchanging a liquid heat-exchange fluid among the above-mentioned gas-liquid separated heat-exchange fluids with ammonia.

9. In paragraph 1, The above S1 step is an ammonia recovery method for separating impurity gas from the mixed gas at a temperature of 20 to 60°C and a pressure of 0 to 3 barg.

10. In paragraph 1, The above S2 step is an ammonia recovery method in which the mixed gas that has passed through the S1 step is cooled to -60 to 0°C at a pressure of 1 to 20 barg to separate the first residual impurity gas.

11. In paragraph 1, The above S3 step is an ammonia recovery method in which the mixed gas that has passed through the S2 step is cooled to -20 to 30°C at a pressure of 1 to 20 barg to separate the second residual impurity gas.

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