Device for producing liquid ammonia through desorption of ammonium phosphate ammonia washing pregnant solution

Abstract

The utility model relates to the technical field of recovery of coking chemical products, in particular to a device for producing liquid ammonia through desorption of ammonium phosphate ammonia washing rich liquor. The upper part and the lower part of the partition plate are respectively connected with an intermediate condenser pipeline of the rectifying section; the hot ammonium phosphate rich solution pipeline is connected with the middle of the desorption tower, the bottom of the desorption tower is connected with the hot ammonium phosphate barren solution pipeline, and the reboiler is arranged at the bottom of the desorption tower; the top of the desorption tower, the dephlegmator, the alkali washer, the ammonia condenser and the gas-liquid separator are sequentially connected through pipelines; the NaOH solution pipeline is connected with the top of the alkaline washer, and the bottom of the alkaline washer is connected with the ammonia distillation process pipeline; the top of the gas-liquid separator is connected with a gas system pipeline before ammonium phosphate ammonia washing, and a liquid ammonia outlet at the bottom of the gas-liquid separator is connected with a subsequent liquid ammonia storage process pipeline. The energy consumption in the desorption process of the ammonium phosphate ammonia washing pregnant solution can be greatly reduced, and meanwhile, an anhydrous liquid ammonia product can be directly produced.

Description

Technical Field

[0001] The utility model relates to the technical field of coking chemical product recovery, in particular to a device for producing liquid ammonia by desorbing ammonia-rich liquid from ammonium phosphate washing. Background Art

[0002] The coke oven gas produced during the coking process contains ammonia as an impurity, and its content is generally 6g to 12g / m 3 . Ammonia impurities in coke oven gas are both corrosive media and important chemical raw materials. From the perspective of corrosiveness, coke oven gas contains a large amount of ammonia, which will be partially absorbed by the washing oil during the process of washing oil to remove benzene and enter the benzene recovery system, which will easily cause the washing oil to emulsify and deteriorate, increase the washing oil consumption, and cause corrosion of the benzene removal equipment and pipelines; from the perspective of chemical raw materials, ammonia can be recycled and made into nitrogen fertilizers, and can also be made into concentrated ammonia water and liquid ammonia and other products for sale and takeaway, increasing the economic benefits of the enterprise.

[0003] The removal and recovery processes of ammonia impurities in coke oven gas mainly include sulfuric acid absorption ammonia production ammonium sulfate process, water washing ammonia production concentrated ammonia water or ammonia decomposition process, phosphate ammonium washing ammonia production concentrated ammonia water or anhydrous ammonia process, etc. Among them, the phosphate ammonium washing ammonia production concentrated ammonia water or anhydrous ammonia process uses phosphate ammonium solution to absorb ammonia in coal gas, while absorbing only trace amounts of acidic components (H2S, HCN, CO2) in coal gas, with good absorption selectivity. Compared with other coal gas deammoniation processes, it has better economic benefits and better market advantages.

[0004] At present, the production of liquid ammonia by washing ammonia with phosphate ammonium is that the coal gas enters the ammonia absorption tower, and contacts with the phosphate ammonium lean liquid sprayed on the top of the tower in countercurrent for chemical absorption. The phosphate ammonium rich liquid after absorbing ammonia is first subjected to tar removal and then heat exchange with the hot phosphate ammonium lean liquid discharged from the desorption tower to a certain temperature before entering the degasser. The phosphate ammonium rich liquid is flashed in the degasser to remove the acidic components. The deacidified phosphate ammonium rich liquid is then heat exchanged with the desorption tower top decompressor and the ammonia vapor at the top of the desorption tower to heat up and enter the desorption tower. The desorption tower is operated at 0.5-1.6MPa, and 1.6MPa direct steam is introduced into the bottom of the tower as stripping steam to strip ammonia in the rich liquid. The concentrated acid vapor partially condensed and concentrated in the decompressor at the top of the desorption tower is condensed into concentrated ammonia water, and then alkali is added to remove trace acidic components and then enters the ammonia distillation tower with an operating pressure of 1.3-1.6MPa for ammonia water stripping and distillation, and a liquid ammonia product is obtained at the top of the tower.

[0005] There are two main problems with the current technology: First, the energy consumption of the ammonium phosphate rich liquid desorption process and the ammonia distillation process is high, accounting for a large proportion of the overall process. When the desorption tower is operated at a medium pressure of 1.3-1.6 MPa, 10-12 tons of medium-pressure steam are consumed for every ton of liquid ammonia obtained when producing anhydrous ammonia; second, there are many factors in the overall process to control the water balance, which is difficult to operate and difficult to achieve. There are three key factors in the existing technology to control the water balance of the overall process system: water brought out by ammonia vapor in the desorption tower, water brought out by coal gas after deammoniation, and water brought in by direct steam from the desorption tower. The water balance of the overall process system can be controlled by adjusting these three key factors. However, these three factors are interrelated. For example, adjusting the amount of direct steam in the desorption tower can easily cause fluctuations in the ammonia vapor concentration at the top of the desorption tower, affecting the subsequent product process, and it is also easy to cause fluctuations in the phosphoric acid concentration in the ammonium phosphate lean liquid, affecting the previous ammonia absorption process. The overall process operation is not flexible and convenient, and excellent production experience is required to control this process, which limits the application of this process.

[0006] A Chinese patent with patent authorization announcement number CN101531379B discloses a "method for producing anhydrous ammonia by phosphate ammonium absorption method", in which the desorption tower bottom heater is indirectly heated by heat transfer oil, which reduces the amount of sewage discharged compared with directly passing steam into the bottom of the desorption tower for desorption of phosphate ammonium rich solution; but the operating pressure of the desorption tower is a low pressure of 0.3 to 0.55 MPa. The low operating pressure of the desorption tower leads to a low temperature of the phosphate ammonium solution in the desorption tower and a low desorption efficiency. Compared with the phosphate ammonium washing ammonia production anhydrous ammonia process using medium pressure 1.4 to 1.6 MPa rich solution desorption, the energy consumption of the desorption process of this utility model method is actually increased, and there is no advantage in process energy saving, and there is no improvement in the convenience of controlling water balance operation.

[0007] The Chinese patent document with patent application publication number CN105293524A discloses a "waste heat recovery system and process for producing anhydrous ammonia from phosphate ammonium washing ammonia", which uses the waste heat of ammonia vapor after the first desorption tower cooler at the top of the desorption tower and the waste heat of phosphate ammonium lean liquid as the heat source for distillation of other process media for coal gas purification, thereby improving the energy utilization rate among various processes in the factory. However, this process does not reduce the steam energy consumption in the desorption process of phosphate ammonium rich liquid, and the steam consumption is still large, and there is no improvement in the convenience of controlling the water balance operation. Utility Model Content

[0008] In order to overcome the shortcomings of the prior art, the utility model provides a device for producing liquid ammonia by desorbing rich liquid of phosphate ammonium washing ammonia, which can greatly reduce the energy consumption of the desorption process of rich liquid of phosphate ammonium washing ammonia, and can directly produce anhydrous liquid ammonia product.

[0009] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0010] A device for producing liquid ammonia by desorbing ammonia-rich liquid for washing with ammonium phosphate, comprises a desorber, an intermediate condenser in a rectifying section, a fractionator, a reboiler, an alkali scrubber, an ammonia condenser and a gas-liquid separator; a partition is arranged in the middle of the rectifying section of the desorber, and the upper and lower parts of the partition are respectively connected to the pipeline of the intermediate condenser in the rectifying section; a hot ammonium phosphate-rich liquid pipeline is connected to the middle of the desorber, the bottom of the desorber is connected to the hot ammonium phosphate-poor liquid pipeline, and a reboiler is arranged at the bottom of the desorber; the top of the desorber, the fractionator, the alkali scrubber, the ammonia condenser and the gas-liquid separator are connected in sequence by pipelines; a NaOH solution pipeline is connected to the top of the alkali scrubber, and the bottom of the alkali scrubber is connected to the pipeline of an ammonia distillation process; the top of the gas-liquid separator is connected to a pipeline of a coal gas system before washing with ammonium phosphate, and the liquid ammonia outlet at the bottom of the gas-liquid separator is connected to a pipeline of a subsequent liquid ammonia storage process.

[0011] Furthermore, the top vapor phase outlet below the partition is connected to the vapor phase inlet pipe of the intermediate condenser of the distillation section; the vapor phase outlet of the intermediate condenser of the distillation section is connected to the bottom vapor phase inlet pipe above this partition; the condensed liquid phase outlet of the intermediate condenser of the distillation section is connected to the top liquid phase inlet pipe below the partition; the bottom liquid phase outlet above the partition is connected to the top liquid phase inlet pipe below this partition.

[0012] Furthermore, the hot ammonium phosphate rich liquid pipeline is connected to the rich liquid inlet pipeline in the middle of the desorption tower; the bottom outlet of the desorption tower is connected to the hot ammonium phosphate lean liquid and the subsequent absorption process pipeline; the alkali liquid outlet at the bottom of the alkali scrubber is connected to the ammonia evaporation process pipeline; the NaOH solution is connected to the alkali liquid inlet pipeline at the top of the alkali scrubber; the non-condensable gas outlet at the top of the gas-liquid separator is connected to the gas system pipeline before the ammonium phosphate washing ammonia; the liquid ammonia outlet at the bottom of the gas-liquid separator is connected to the subsequent liquid ammonia storage process pipeline.

[0013] Furthermore, the desorbed ammonia vapor outlet at the top of the desorber is connected to the vapor phase inlet pipeline of the fractionator; the liquid phase outlet of the fractionator is connected to the liquid phase inlet at the top of the desorber; the ammonia gas outlet of the fractionator is connected to the ammonia gas inlet of the alkali scrubber; the ammonia outlet at the top of the alkali scrubber is connected to the ammonia gas inlet pipeline of the ammonia condenser; the liquid ammonia outlet of the ammonia condenser is connected to the liquid ammonia inlet pipeline at the top of the gas-liquid separator.

[0014] Furthermore, the alkali washer is of packing type or plate type.

[0015] Compared with the prior art, the beneficial effects of the utility model are:

[0016] 1. The utility model sets a rectifying section intermediate condenser in the middle of the rectifying section of the desorber, and sets a fractionator at the top of the desorber, and partially condenses the desorbed ammonia vapor rising in the rectifying section of the desorber in two steps, controls the cooling heat exchange amount, and thus can further concentrate the ammonia vapor concentration. Compared with the prior art, the ammonia vapor concentration after the top of the phosphate ammonium rich liquid desorption tower is controlled at 18% to 25%. The utility model can directly produce high-purity ammonia gas of 99.9% to 99.99% after the desorber, and then make a liquid ammonia product through alkali washing and condensation, without the need for the ammonia distillation process required in the prior art, thereby reducing equipment investment and shortening and simplifying the process flow.

[0017] 2. The utility model sets an intermediate condenser of the distillation section in the middle of the distillation section of the desorption tower, so as to recover the heat released by the partial condensation of ammonia vapor in the distillation section with waste heat, and use it in the processes such as ammonia evaporation in the coking plant, thereby improving the energy utilization rate of the coking plant, which also greatly reduces the consumption of circulating water; at the same time, compared with the existing technology of producing anhydrous ammonia by washing ammonia with phosphate ammonium, the utility model also reduces the ammonia distillation process, reduces the consumption of heat and cooling in the ammonia distillation process; therefore, in terms of energy saving, the comprehensive energy consumption of the utility model is greatly reduced, thereby reducing the operating cost of the coking enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure and process principle of the utility model.

[0019] In the figure: 1-desorption tower, 2-intermediate condenser of distillation section, 3-contractor, 4-reboiler, 5-alkali scrubber, 6-ammonia condenser, 7-gas-liquid separator, 101-partition. DETAILED DESCRIPTION

[0020] The embodiments of the present invention are described in detail below. In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described in combination with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0022] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] In the description of the utility model, it should be noted that the terms used herein are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the utility model. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0024] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, the numerical expressions and numerical values ​​do not limit the scope of the utility model. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0025] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the utility model.

[0026] like Figure 1 As shown, a device for desorbing ammonia-rich liquid from phosphate ammonium washing to produce liquid ammonia comprises a desorption tower 1, an intermediate condenser 2 in the rectification section, a fractionator 3, a reboiler 4, an alkali scrubber 5, an ammonia condenser 6, a gas-liquid separator and connecting pipes.

[0027] A partition 101 is provided in the middle of the rectifying section of the desorption tower 1, and the top vapor phase outlet below the partition 101 is connected to the vapor phase inlet pipeline of the rectifying section intermediate condenser 2. The vapor phase outlet of the rectifying section intermediate condenser 2 is connected to the bottom vapor phase inlet pipeline above the partition 101; the condensed liquid phase outlet of the rectifying section intermediate condenser 2 is connected to the top liquid phase inlet pipeline below the partition 101. The bottom liquid phase outlet above the partition 101 is connected to the top liquid phase inlet pipeline below the partition 101.

[0028] The hot ammonium phosphate rich liquid pipeline is connected to the rich liquid inlet pipeline in the middle of the desorption tower 1, the hot ammonium phosphate lean liquid at the bottom of the desorption tower 1 is connected to the pipeline of the subsequent absorption process, and a reboiler 4 is arranged at the bottom of the desorption tower 1.

[0029] The desorbed ammonia vapor outlet at the top of the desorber 1 is connected to the vapor phase inlet pipeline of the fractionator 3, the liquid phase outlet of the fractionator 3 is connected to the liquid phase inlet at the top of the desorber 1, the ammonia gas outlet of the fractionator 3 is connected to the ammonia gas inlet of the alkali scrubber 5, the alkali liquid outlet at the bottom of the alkali scrubber 5 is connected to the ammonia distillation process pipeline, the NaOH solution is connected to the alkali liquid inlet pipeline at the top of the alkali scrubber 5, the ammonia outlet at the top of the alkali scrubber 5 is connected to the ammonia gas inlet pipeline of the ammonia condenser 6, and the liquid ammonia outlet of the ammonia condenser 6 is connected to the liquid ammonia inlet pipeline at the top of the gas-liquid separator 7.

[0030] The non-condensable gas outlet at the top of the gas-liquid separator 7 is connected to the gas system pipeline before the phosphate ammonium washing ammonia; the liquid ammonia outlet at the bottom of the gas-liquid separator 7 is connected to the pipeline of the subsequent liquid ammonia storage process.

[0031] The process principle and working process of the utility model are as follows:

[0032] 1. Condensation and heat exchange in the middle of the rectifying section of the desorption tower. The phosphate-ammonia rich liquid sent from the phosphate-ammonia washing process enters the lean-rich liquid heat exchanger after removing the acid vapor, and then exchanges heat with the phosphate-ammonia lean liquid discharged from the bottom of the desorption tower 1, and then enters the middle of the desorption tower 1; a partition 101 is arranged in the middle of the rectifying section of the desorption tower 1, and the rising hot ammonia vapor at the top below the partition 101 is led out by a side line to enter the intermediate condenser 2 of the rectifying section to exchange heat with the waste hot water for partial condensation, and the partially condensed vapor phase enters the vapor phase inlet at the bottom above the partition 101, and the partially condensed liquid ammonia water enters the ammonia water inlet at the top below the partition 101; the descending liquid ammonia water at the bottom above the partition 101 flows into the ammonia water inlet at the top below the partition 101 along the pipeline, and this pipeline is provided with a U-shaped liquid seal; a reboiler 4 is arranged at the bottom of the desorption tower 1, and the desorption operation is provided with heat for the desorption tower 1 by an external heat source through the reboiler 4. The operating pressure at the top of the desorption tower 1 is 1000 kPag to 1800 kPag, the vapor phase temperature after partial condensation in the intermediate condenser 2 of the distillation section is 120° C. to 70° C., and the mass fraction of ammonia in the ammonia gas discharged from the fractionator 3 is 99.9 to 99.99%.

[0033] 2. Partial condensation and reflux of ammonia vapor at the top of the desorption tower. The ammonia vapor at the top of the desorption tower 1 enters the fractionator 3 for heat exchange with circulating water and partial condensation. The partially condensed vapor phase is ammonia gas and enters the subsequent ammonia product process; the partially condensed liquid phase refluxes to the top of the desorption tower 1 as the liquid phase reflux of the distillation section.

[0034] 3. Ammonia gas is alkali-eluted to remove acidic components. The ammonia gas after the decompressor 3 enters the bottom of the alkali washer 5 and contacts with the NaOH solution entering from the top of the alkali washer 5 in countercurrent gas-liquid manner to absorb the acidic components. The trace acidic components H2S, HCN and CO2 in the ammonia gas are absorbed. The NaOH solution after absorbing the acidic components is discharged to the coking ammonia distillation unit to decompose the fixed ammonium in the remaining ammonia water.

[0035] 4. Ammonia gas is condensed and separated from gas and liquid. After alkali washing, the ammonia gas enters the ammonia condenser 6 for heat exchange with circulating water to condense into liquid ammonia, and then enters the gas-liquid separator to separate the non-condensable gas. The non-condensable gas phase separated by the gas-liquid separator 7 is discharged to the gas system before phosphate ammonium washing ammonia. The liquid ammonia after separation of the non-condensable gas enters the subsequent liquid ammonia storage process as a product.

[0036] The utility model can greatly reduce the energy consumption in the desorption process of the ammonium phosphate washing ammonia rich liquid, and can directly produce anhydrous liquid ammonia products.

[0037] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes within the technical scope disclosed by the present invention according to the technical scheme and the utility model concept of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A device for producing liquid ammonia by desorbing ammonia-rich liquid from ammonium phosphate washing, characterized in that: It includes a desorption tower, an intermediate condenser in the rectification section, a fractionator, a reboiler, an alkali scrubber, an ammonia condenser and a gas-liquid separator; A partition is arranged in the middle of the distillation section of the desorption tower, and the upper and lower parts of the partition are respectively connected to the pipeline of the middle condenser of the distillation section; The hot ammonium phosphate rich liquid pipeline is connected to the middle of the desorption tower, the bottom of the desorption tower is connected to the hot ammonium phosphate lean liquid pipeline, and a reboiler is arranged at the bottom of the desorption tower; The top of the desorption tower, the fractionator, the alkali scrubber, the ammonia condenser, and the gas-liquid separator are sequentially connected by pipelines; The NaOH solution pipeline is connected to the top of the alkali scrubber, and the bottom of the alkali scrubber is connected to the ammonia distillation process pipeline; the top of the gas-liquid separator is connected to the gas system pipeline before phosphate ammonium washing ammonia, and the liquid ammonia outlet at the bottom of the gas-liquid separator is connected to the subsequent liquid ammonia storage process pipeline.

2. The device for producing liquid ammonia by desorbing rich liquid of ammonium phosphate washing according to claim 1, characterized in that: The top vapor phase outlet below the partition is connected to the vapor phase inlet pipeline of the intermediate condenser of the rectifying section; the vapor phase outlet of the intermediate condenser of the rectifying section is connected to the bottom vapor phase inlet pipeline above the partition; The condensed liquid phase outlet of the intermediate condenser in the distillation section is connected to the top liquid phase inlet pipeline below the partition; the bottom liquid phase outlet above the partition is connected to the top liquid phase inlet pipeline below the partition.

3. The device for producing liquid ammonia by desorbing rich liquid of ammonium phosphate washing according to claim 1, characterized in that: The hot ammonium phosphate rich liquid pipeline is connected to the rich liquid inlet pipeline in the middle of the desorption tower; the bottom outlet of the desorption tower is connected to the hot ammonium phosphate lean liquid and the subsequent absorption process pipeline; the alkali liquid outlet at the bottom of the alkali scrubber is connected to the ammonia distillation process pipeline; the NaOH solution is connected to the alkali liquid inlet pipeline at the top of the alkali scrubber; the non-condensable gas outlet at the top of the gas-liquid separator is connected to the gas system pipeline before the ammonium phosphate washing ammonia; the liquid ammonia outlet at the bottom of the gas-liquid separator is connected to the subsequent liquid ammonia storage process pipeline.

4. The device for producing liquid ammonia by desorbing rich liquid of ammonium phosphate washing according to claim 1, characterized in that: The desorbed ammonia vapor outlet at the top of the desorber is connected to the vapor phase inlet pipeline of the fractionator; the liquid phase outlet of the fractionator is connected to the liquid phase inlet at the top of the desorber; the ammonia gas outlet of the fractionator is connected to the ammonia gas inlet of the alkali scrubber; the ammonia outlet at the top of the alkali scrubber is connected to the ammonia gas inlet pipeline of the ammonia condenser; the liquid ammonia outlet of the ammonia condenser is connected to the liquid ammonia inlet pipeline at the top of the gas-liquid separator.

5. The device for producing liquid ammonia by desorbing rich ammonia solution from ammonium phosphate washing according to claim 1, characterized in that: The alkali washer is of filler type or plate type.

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