Ammonia water treatment method, ammonia water treatment facility, and method for producing concentrated ammonia water

Abstract

Provided are an ammonia water treatment method and the like with which it is possible to utilize ammonia water obtained from a coke oven gas for a variety of applications. Specifically, a method for treating ammonia water obtained from a coke oven gas is provided. The ammonia water treatment method comprises: a first concentration step for concentrating ammonia water obtained from a coke oven gas; and a second concentration step for concentrating the ammonia water concentrated in the first concentration step. The ammonia water treatment method according to the present invention can be used, for example, for applications such as combusting ammonia water obtained from a coke oven gas. Thus, the ammonia water treatment method according to the present invention makes it possible to use ammonia water obtained from a coke oven gas in a variety of applications. This makes it possible to increase business profit by selecting a product to be produced according to the current price of the target product.

Description

Method for treating ammonia water, ammonia water treatment equipment, and method for producing concentrated ammonia water

[0001] The present invention relates to a method for treating ammonia water obtained from coke oven gas, ammonia water treatment equipment, and a method for producing concentrated ammonia water.

[0002] Ammonia water obtained from coke oven gas is treated, for example, in Patent Document 1 as follows. First, ammonia and acid gas are removed in an ammonia water stripper. Next, the vapor discharged from the ammonia water stripper is condensed. Finally, ammonia in the condensed liquid is removed in a deammoniation facility. In the deammoniation facility, ammonia is recovered as a useful product such as ammonium sulfate or liquid ammonia.

[0003] Japanese Patent Application Laid-Open No. 61-83291

[0004] However, since the production of ammonium sulfate requires a large amount of sulfuric acid, the amount of sulfuric acid obtained from desulfurization of coke oven gas alone is insufficient, which causes the problem of increased treatment costs. In addition, production of liquid ammonia has the problem that a large number of auxiliary facilities must be installed. As described above, conventional treatment of ammonia water obtained from coke oven gas requires a great deal of labor and cost, so further expansion of its application is desired.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a method for treating ammonia water and the like that enable ammonia water obtained from coke oven gas to be used for various applications.

[0006] In order to solve the above problems, the present invention has the following features.

[0007] [1] A method for treating ammonia water obtained from coke oven gas, comprising: a first concentration step of concentrating the ammonia water obtained from the coke oven gas; and a second concentration step of concentrating the ammonia water concentrated in the first concentration step. [2] The method for treating ammonia water according to [1], further comprising a combustion step of burning the ammonia water obtained in the second concentration step. [3] The method for treating ammonia water according to [2], wherein the heat obtained in the combustion step is used in the second concentration step. [4] The method for treating ammonia water according to [2] or [3], wherein the concentration of the ammonia water obtained in the second concentration step is 20% by mass or more. [5] The method for treating ammonia water according to [1] to [4], further comprising a reduction step of reducing nitrogen oxides using the ammonia water obtained in the second concentration step. [6] The method for treating ammonia water according to [1] to [5], further comprising an ammonium sulfate production step of producing ammonium sulfate using a portion of the ammonia water obtained in the first concentration step. [7] The method for treating ammonia water according to any one of [1] to [6], wherein the first concentration step is performed in a reduced pressure environment. [8] A treatment apparatus for ammonia water obtained from coke oven gas, comprising: a first concentration section for concentrating the ammonia water obtained from the coke oven gas; and a second concentration section for concentrating the ammonia water concentrated in the first concentration section. [9] A method for producing concentrated ammonia water from ammonia water obtained from coke oven gas, comprising: a first concentration step for concentrating the ammonia water obtained from the coke oven gas; and a second concentration step for concentrating the ammonia water concentrated in the first concentration step.

[0008] The ammonia water treatment method according to the present invention comprises a first concentration step of concentrating ammonia water obtained from coke oven gas, and a second concentration step of concentrating the ammonia water concentrated in the first concentration step. Therefore, it can be used, for example, for burning ammonia water obtained from coke oven gas. In this way, the ammonia water treatment method according to the present invention makes it possible to utilize ammonia water obtained from coke oven gas for a variety of uses. This makes it possible to improve business profits by selecting the products to be produced according to the market price of the target products.

[0009] This is an explanatory diagram showing an overview of the ammonia water treatment equipment. This is an explanatory diagram showing an overview of the first concentration section in Figure 1. This is a flow chart of the ammonia water treatment method. This is a flow chart of the ammonia water treatment method according to Modification Example 1. This is a flow chart of the ammonia water treatment method according to Modification Example 2.

[0010] The present invention will be described below through embodiments of the invention. Figure 1 shows an overview of the ammonia water treatment equipment 100. The ammonia water treatment equipment 100 includes a first concentration unit 10 for concentrating ammonia water obtained from coke oven gas, and a second concentration unit 20 for concentrating the ammonia water concentrated in the first concentration unit 10.

[0011] The first concentration unit 10 and the second concentration unit 20 are ammonia strippers that concentrate ammonia water. The first concentration unit 10 is connected to an ammonia water storage unit 40 that stores ammonia water treated in the coke oven gas processing unit 30.

[0012] More specifically, in a coke oven (not shown), coke is produced by carbonization of coal. During this process, coal tar, coke oven gas, and ammonia water are generated as by-products.

[0013] In the coke oven gas processing unit 30, these by-products are separated. The coke oven gas is supplied to the ammonium sulfate production unit 50 located in the coke oven gas purification line. Coal tar and ammonia water are separated in the coke oven gas processing unit 30 by difference in specific gravity. The separated ammonia water is supplied to the ammonia water storage unit 40.

[0014] The first concentration unit 10 concentrates the ammonia water supplied from the ammonia water storage unit 40. The first concentration unit 10 is connected to the second concentration unit 20 and the ammonium sulfate production unit 50. The ammonia water concentrated in the first concentration unit 10 is supplied to the second concentration unit 20 and the ammonium sulfate production unit 50.

[0015] The second concentration unit 20 is connected to an ammonia water recovery unit 60, which recovers the ammonia water concentrated in the second concentration unit 20. The ammonia water recovered in the ammonia water recovery unit 60 is supplied to the combustion unit 70.

[0016] The combustion unit 70 burns the ammonia water recovered in the ammonia water recovery unit 60. The combustion unit 70 is not particularly limited, but for example, a combustion furnace having a burner for burning fuel gas can be used.

[0017] While there are no particular limitations on the type of combustion furnace, for example, one that burns flammable gases such as benzene and naphthalene generated in chemical plants along with the fuel can be used.

[0018] When ammonia water burns in the combustion section 70, the combustion exhaust gas is used to recover heat as steam in an attached boiler or the like. The heat recovered in the boiler or the like may be supplied as steam to the second concentration section 20, for example. This improves the thermal efficiency of the second concentration section 20.

[0019] The second concentration unit 20 is connected to a treated water recovery unit 80 that recovers the treated water generated during concentration. The treated water recovered in the treated water recovery unit 80 is supplied, for example, to the first concentration unit 10.

[0020] Figure 2 shows an overview of the first concentration unit 10. As shown in Figure 2, it has an ammonia stripper body 11 formed in the shape of a container. An ammonia water storage unit 40 and a steam supply unit 12 are connected to the ammonia stripper body 11.

[0021] The ammonia stripper body 11 is designed to allow steam to be extracted from the top. A condenser 13 is connected to the ammonia stripper body 11. A vacuum pump 14 is also connected to the ammonia stripper body 11 via the condenser 13.

[0022] The ammonia stripper body 11 is depressurized by a vacuum pump 14. When ammonia water and steam are supplied to the ammonia stripper body 11 from the ammonia water storage section 40 and the steam supply section 12, the ammonia vaporizes and is concentrated in the condenser 13.

[0023] The ammonia water concentrated in the condenser 13 is supplied to the second concentration unit 20. The second concentration unit 20 has the same configuration as the first concentration unit 10. The treated water obtained when the ammonia water is concentrated in the second concentration unit 20 is supplied to, for example, the vacuum pump 14.

[0024] The treated water obtained in the second concentration unit 20 is dilute water with an ammonia concentration of 50 ppm or less. Furthermore, this treated water does not contain metals such as calcium that would form salts. Therefore, by using this treated water as the sealing water for the vacuum pump 14, unlike when using industrial water or purified water, the formation of salts can be suppressed. As a result, an increase in wastewater treatment volume can be prevented, and running costs can be reduced.

[0025] Furthermore, the ammonia water vapor that has passed through the vacuum pump 14 is supplied to the ammonium sulfate generation unit 50.

[0026] Figure 3 shows the flow of the ammonia water treatment method. As shown in Figure 3, the ammonia water that has passed through the coke oven gas treatment section 30 and the ammonia water storage section 40 is concentrated in the first concentration section 10. That is, a first concentration step is performed to concentrate the ammonia water obtained from the coke oven gas (step S01).

[0027] In the first concentration step of step S01, ammonia water is supplied from the ammonia water storage unit 40 to the first concentration unit 10 at a supply rate of, for example, 60 t / h. The concentration of the ammonia water at this time is not particularly limited, but for example, it is 6500 mg / l.

[0028] In the first concentration step of step S01, the vacuum pump 14 sets the environment to a reduced pressure of, for example, 150 Torr (19998.4 Pa). At the above concentration of ammonia water, the boiling point of the ammonia water is approximately 60°C. Steam is supplied from the steam supply unit 12 so that the ammonia water supplied from the ammonia water storage unit 40 reaches a temperature above the boiling point, for example, 65°C or higher. The ammonia water concentrated in the first concentration step of step S01 is not particularly limited, but for example, it has a concentration of 3 to 6% by mass.

[0029] Next, the ammonia water obtained in the first concentration step of step S01 is concentrated in the second concentration section 20 in a second concentration step (step S02). Preferably, the concentration of the ammonia water obtained in the second concentration step of step S02 is 20% by mass or more. A concentration of 20% by mass or more of the ammonia water makes it easier to burn the ammonia in the subsequent combustion step.

[0030] There is no particular upper limit to the concentration of the ammonia water, but if the concentration becomes excessively high, the time and effort required to concentrate the ammonia water will increase. For this reason, the concentration of the ammonia water obtained in the second concentration step of step S02 is preferably 20 to 40% by mass, more preferably 20 to 35% by mass, and even more preferably 20 to 25% by mass. In other words, concentrated ammonia water is produced by carrying out the first concentration step of step S01 and the second concentration step of step S02.

[0031] Finally, the ammonia water concentrated in the second concentration step is recovered as concentrated ammonia water in the ammonia water recovery unit 60 and a combustion step is performed in the combustion unit 70 (step S03).

[0032] In the combustion process of step S03, aqueous ammonia is supplied to the combustion furnace, for example, by spraying. Since ammonia does not contain carbon as a constituent element, it does not produce carbon dioxide when burned. This makes it possible to process ammonia without generating carbon dioxide.

[0033] In the combustion process of step S03, for example, the ammonia water may be sprayed onto the part of the combustion furnace that is 1050°C or higher. By burning ammonia water in this temperature range, it is possible to suppress the generation of nitrogen oxides.

[0034] Furthermore, the waste gas produced by burning ammonia water in the combustion process of step S03 may be recovered as steam using an attached boiler. When recovering the steam, although not particularly limited, it is preferable to set the boiler's set pressure (saturated steam) to 0.8 MPa. The recovered steam may be used in the second concentration process. By reusing heat in this way, energy consumption can be reduced.

[0035] The ammonia water treatment method according to the present invention comprises a first concentration step of concentrating ammonia water obtained from coke oven gas, and a second concentration step of concentrating the ammonia water concentrated in the first concentration step. Therefore, it can be used, for example, for applications such as burning ammonia water obtained from coke oven gas.

[0036] (Modification 1) In the above embodiment, the ammonia water concentrated in the second concentration step of step S02 was used to perform the combustion step of step S03. The ammonia water concentrated in the second concentration step of step S02 is not limited to this use and may also be used for the reduction of nitrogen oxides.

[0037] Figure 4 shows a flow chart of the ammonia water treatment method according to Modification 1. As shown in Figure 4, the ammonia water that has passed through the coke oven gas treatment section 30 and the ammonia water storage section 40 is concentrated in the first concentration section 10. That is, a first concentration step is performed to concentrate the ammonia water obtained from the coke oven gas (step S01). The first concentration step in step S01 is the same as in the embodiment described above, so its explanation is omitted.

[0038] Next, the aqueous ammonia obtained in the first concentration step of step S01 is concentrated in the second concentration section 20 in a second concentration step (step S02). The second concentration step of step S02 is the same as in the embodiment described above, so its explanation is omitted.

[0039] Next, the ammonia water concentrated in the second concentration step is recovered in the ammonia water recovery unit 60 and burned in the combustion unit 70 in a combustion step (step S03). The combustion step in step S03 is the same as in the embodiment described above, so its explanation is omitted.

[0040] Finally, the nitrogen oxides generated in the combustion step of step S03 are reduced using the concentrated ammonia water in the second concentration step of step S02, thereby performing a reduction step (step S04). In this embodiment, the nitrogen oxides used in the reduction step of step S04 are described as being used to reduce the nitrogen oxides generated in step S03. However, the reduction step of step S04 is not limited to the nitrogen oxides generated in step S03; that is, nitrogen oxides can be reduced regardless of their source. Alternatively, instead of the reduction step of step S04, the ammonia water recovered in the ammonia water recovery unit 60 may be sold or otherwise transferred.

[0041] (Modification 2) In the above-described embodiment, the ammonia water obtained in the first concentration step of step S01 is used in the second concentration step of the second concentration unit 20. The ammonia water obtained in the first concentration step of step S01 is not limited to this use and may be used for other purposes.

[0042] FIG. 5 shows a flow of a method for treating ammonia water according to Modification 2. As shown in FIG. 5, the ammonia water that has passed through a coke oven gas treatment unit 30 and an ammonia water storage unit 40 is concentrated in a first concentrating unit 10. That is, a first concentration step of concentrating the ammonia water obtained from coke oven gas is performed (step S01). Since the first concentration step of step S01 is the same as that in the above-described embodiment, the description thereof is omitted.

[0043] Next, a part of the ammonia water obtained in the first concentration step of step S01 is supplied to an ammonium sulfate production unit 50, and an ammonium sulfate production step for producing ammonium sulfate is performed (step S05).

[0044] As described above, the method for treating ammonia water according to the present invention enables the ammonia water obtained from coke oven gas to be used for various applications. This makes it possible to improve business revenue by selecting a product to be produced according to the market price of the target product. That is, the ammonia water treatment facility is preferably configured such that an ammonia water supply line can be appropriately selected according to the use of the ammonia water.

[0045] For example, when ammonium sulfate is more profitable than other treatment modes, it is preferable to produce ammonium sulfate. In addition, when it is more profitable to recover steam by combusting ammonia water than other treatment modes, it is preferable to combust the ammonia water. In this way, the treatment method may be selected by comparing the profitability with other treatments.

[0046] For example, when combusting ammonia water, the amount of sulfuric acid used when producing ammonium sulfate can be reduced. Thereby, the sulfuric acid produced from the coke oven gas can be used for other purposes such as sale.

[0047] In the embodiments described above, the first concentration unit 10 and the second concentration unit 20 were described as examples in which they are vacuum ammonia strippers. The first concentration unit 10 and the second concentration unit 20 are not limited to vacuum ammonia strippers, but may be composed of atmospheric pressure ammonia strippers. Even with this configuration, the same effects and advantages as in the embodiments described above can be obtained.

[0048] 100 Ammonia water treatment equipment 10 First concentration section 20 Second concentration section 70 Combustion section

Claims

1. A method for treating ammonia water obtained from coke oven gas, comprising: a first concentration step of concentrating the ammonia water obtained from the coke oven gas; and a second concentration step of concentrating the ammonia water concentrated in the first concentration step.

2. The method for treating ammonia water according to claim 1, further comprising a combustion step of burning the ammonia water obtained in the second concentration step.

3. The method for treating ammonia water according to claim 2, wherein the heat obtained in the combustion step is used in the second concentration step.

4. The method for treating ammonia water according to claim 2 or 3, wherein the concentration of the ammonia water obtained in the second concentration step is 20% by mass or more.

5. A method for treating ammonia water according to any one of claims 1 to 4, further comprising a reduction step of reducing nitrogen oxides using the ammonia water obtained in the second concentration step.

6. A method for treating aqueous ammonia according to any one of claims 1 to 5, comprising an ammonium sulfate production step of producing ammonium sulfate using a portion of the aqueous ammonia obtained in the first concentration step.

7. The method for treating aqueous ammonia according to any one of claims 1 to 6, wherein the first concentration step is performed under reduced pressure.

8. A treatment apparatus for ammonia water obtained from coke oven gas, comprising: a first concentration unit for concentrating the ammonia water obtained from the coke oven gas; and a second concentration unit for concentrating the ammonia water concentrated in the first concentration unit.

9. A method for producing concentrated ammonia water from ammonia water obtained from coke oven gas, comprising: a first concentration step of concentrating the ammonia water obtained from the coke oven gas; and a second concentration step of concentrating the ammonia water concentrated in the first concentration step.

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