Ammonia stripping method urea production process low pressure system and ammoniation method

Abstract

The present application relates to urea production technical field, disclose a kind of ammonia stripping method urea production process low-pressure system and ammoniation method, the ammonia stripping method urea production process low-pressure system, including middle-pressure inert gas washing tower, the bottom of the middle-pressure inert gas washing tower is connected with ammonia water pump, the discharge end of the ammonia water pump is connected with low-pressure carbonammonium liquid storage tank;The feeding pipeline and dilute ammonia pipeline are sequentially communicated between the ammonia water pump and the low-pressure carbonammonium liquid storage tank, the discharge end of the feeding pipeline is connected with middle-pressure absorption tower, the dilute ammonia pipeline is connected with the middle section of the feeding pipeline away from the low-pressure carbonammonium liquid storage tank one end.The low-pressure system and ammoniation method of the present application, by setting and improving the arrangement of pipeline, can simplify urea production device empty tower commissioning before low-pressure system ammoniation process, and reduce the loss of venting ammonia and environmental pollution caused by low-pressure system ammoniation.

Description

Technical Field

[0001] This invention relates to the field of urea production technology, and more specifically, to a low-pressure system and ammoniation method for ammonia stripping urea production process. Background Technology

[0002] Urea production units typically employ the ammonia stripping urea production process. Before the high-pressure system of the unit is started up in the empty tower, the low-pressure system needs to be ammonified. This means that at the initial stage of start-up, dilute ammonia water is prepared to absorb CO2 gas in the system, and ammonia water is used as the ammonification material.

[0003] In the ammonia stripping urea production process, the steps for preparing the aforementioned dilute ammonia solution are as follows: liquid ammonia from the liquid ammonia storage tank is pumped to a medium-pressure absorption tower via an ammonia booster pump; the liquid ammonia is absorbed by the flushing water from the absorption tower trays; and then discharged through the discharge valve of the medium-pressure scrubbing tower to a low-pressure ammonium carbonate solution storage tank. To control the ammonia concentration, a liquid circulation system needs to be established, connecting the low-pressure ammonium carbonate solution storage tank to the low-pressure ammonium carbonate solution pump, then to the condenser, and finally back to the low-pressure ammonium carbonate solution storage tank. However, this process generates significant heat, resulting in substantial ammonia venting from the low-pressure system, leading to significant ammonia gas loss and causing considerable environmental pollution.

[0004] Existing urea production units have long been processing dilute ammonia solution and sending it to the synthetic ammonia water section. Specifically, the gaseous ammonia in the liquid ammonia storage tank is absorbed by a medium-pressure inert gas scrubbing tower with washing water to prepare dilute ammonia solution, which is then pumped to the synthetic ammonia water station. The concentration is typically controlled at 20-25 wt%. During normal operation of the urea production unit, a portion of the recovered dilute ammonia solution is pumped back to the urea medium-pressure absorption tower for reuse. This process requires the simultaneous and continuous operation of a large number of devices, resulting in a complex process flow, cumbersome operation, heavy production burden, and severe equipment wear and tear. Summary of the Invention

[0005] The technical problem to be solved by this invention: Currently, in the ammonia stripping urea production process, the ammoniation process in the low-pressure system of the urea production unit is relatively complex. It requires many devices to operate simultaneously or continuously, making the operation cumbersome. Furthermore, the large amount of heat generated during the ammoniation process causes gaseous ammonia to be released into the low-pressure system, resulting in significant material loss and serious environmental pollution.

[0006] The technical solution adopted in this invention is as follows: This invention provides a low-pressure system for ammonia stripping urea production process, including a medium-pressure inert gas scrubbing tower. An ammonia pump is connected to the bottom of the medium-pressure inert gas scrubbing tower, and the outlet of the ammonia pump is connected to a low-pressure ammonium bicarbonate liquid storage tank. A feeding pipeline and a dilute ammonia pipeline are sequentially connected between the ammonia pump and the low-pressure ammonium bicarbonate liquid storage tank. The outlet of the feeding pipeline is connected to a medium-pressure absorption tower, and the end of the dilute ammonia pipeline furthest from the low-pressure ammonium bicarbonate liquid storage tank is connected to the middle section of the feeding pipeline.

[0007] Preferably, the low-pressure ammonium bicarbonate solution storage tank is equipped with a low-pressure feed pipeline, and one end of the dilute ammonia water pipeline near the low-pressure ammonium bicarbonate solution storage tank is connected to the middle section of the low-pressure feed pipeline.

[0008] Preferably, the low-pressure feed pipeline is equipped with a low-pressure washing water regulating valve, which is located on the side away from the low-pressure ammonium bicarbonate liquid storage tank at the connection between the dilute ammonia water pipeline and the low-pressure feed pipeline.

[0009] Preferably, the top of the low-pressure ammonium bicarbonate liquid storage tank is also equipped with a low-pressure venting pipeline, and the low-pressure venting pipeline is equipped with a low-pressure venting pressure regulating valve.

[0010] Preferably, the feeding pipeline is equipped with an inert gas scrubbing tower level regulating valve, which is located at the connection point between the feeding pipeline and the dilute ammonia water pipeline on the side near the ammonia water pump.

[0011] Preferably, the end of the feeding pipeline near the ammonia pump is also connected to a return pipeline and an ammonia delivery pipeline, the end of the return pipeline away from the feeding pipeline is connected to the medium-pressure inert gas scrubbing tower, and the end of the ammonia delivery pipeline away from the feeding pipeline is connected to the ammonia station.

[0012] Preferably, the feeding pipeline, the dilute ammonia water pipeline, the low-pressure feed pipeline, and the low-pressure venting pipeline are all equipped with at least one manual valve.

[0013] An ammoniation method for urea production using the ammonia stripping process employing the aforementioned low-pressure system includes the following steps: S1 uses a medium-pressure inert gas scrubbing tower to prepare dilute ammonia water; S2 discharges the dilute ammonia water from the bottom of the medium-pressure inert gas scrubbing tower and sends it to the low-pressure system via the ammonia water pump, through the feed pipeline and the dilute ammonia water pipeline. In the low-pressure system, dilute ammonia water is introduced from the dilute ammonia water pipeline and merged with the low-pressure washing water in the low-pressure feed pipeline. The mixture is then introduced into the low-pressure ammonium bicarbonate liquid storage tank for cooling.

[0014] Preferably, the concentration of dilute ammonia water is controlled at 25-35%.

[0015] Preferably, a low-pressure venting pressure regulating valve is used to regulate the pressure of the low-pressure system.

[0016] The beneficial effects of this invention are as follows: The low-pressure system for the ammonia stripping urea production process of this invention, through improved pipeline layout to adjust the material handling process, is simpler to operate and has a more convenient process flow compared to the low-pressure system in traditional urea production units, thereby effectively shortening the production cycle. Using this low-pressure system for ammoniation treatment can fully utilize materials and equipment facilities, reduce unnecessary ammonia loss during the ammoniation process in the low-pressure system, and effectively reduce pollution caused by ammonia venting. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the low-pressure system in the ammonia stripping urea production process of Example 1.

[0018] Attached diagram labels: 1-Medium-pressure inert gas scrubbing tower, 2-Ammonia water pump, 21-Feeding pipeline, 211-Inert gas scrubbing tower level regulating valve, 22-Dilute ammonia water pipeline, 23-Return pipeline, 24-Ammonia delivery pipeline, 3-Low-pressure ammonium bicarbonate liquid storage tank, 31-Low-pressure feed pipeline, 311-Low-pressure scrubbing water regulating valve, 32-Low-pressure venting pipeline, 321-Low-pressure venting pressure regulating valve, 4-Medium-pressure absorption tower, 5-Ammonia water station, 6-Manual valve. Detailed Implementation

[0019] To make the objectives, 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 below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] This invention provides a low-pressure system for ammonia stripping urea production process, including a medium-pressure inert gas scrubbing tower 1, an ammonia pump 2 connected to the bottom of the medium-pressure inert gas scrubbing tower 1, and a low-pressure ammonium bicarbonate liquid storage tank 3 connected to the outlet end of the ammonia pump 2; a feeding pipeline 21 and a dilute ammonia pipeline 22 are connected sequentially between the ammonia pump 2 and the low-pressure ammonium bicarbonate liquid storage tank 3, the outlet end of the feeding pipeline 21 is connected to a medium-pressure absorption tower 4, and the end of the dilute ammonia pipeline 22 away from the low-pressure ammonium bicarbonate liquid storage tank 3 is connected to the middle section of the feeding pipeline 21.

[0021] In this invention, the low-pressure ammonium bicarbonate solution storage tank 3 is equipped with a low-pressure feed pipeline 31, and the end of the dilute ammonia water pipeline 22 near the low-pressure ammonium bicarbonate solution storage tank 3 is connected to the middle section of the low-pressure feed pipeline 31. The low-pressure feed pipeline 31 is equipped with a low-pressure washing water regulating valve 311, which is located on the side away from the low-pressure ammonium bicarbonate solution storage tank 3 at the connection between the dilute ammonia water pipeline 22 and the low-pressure feed pipeline 31. The top of the low-pressure ammonium bicarbonate solution storage tank 3 is also equipped with a low-pressure vent pipeline 32, which is equipped with a low-pressure vent pressure regulating valve 321.

[0022] In this invention, the feeding pipeline 21 is equipped with an inert gas scrubbing tower level regulating valve 211, which is located near the ammonia pump 2 at the connection between the feeding pipeline 21 and the dilute ammonia water pipeline 22. The end of the feeding pipeline 21 near the ammonia pump 2 is also connected to a return pipeline 23 and an ammonia delivery pipeline 24. The end of the return pipeline 23 away from the feeding pipeline 21 is connected to the medium-pressure inert gas scrubbing tower 1, and the end of the ammonia delivery pipeline 24 away from the feeding pipeline 21 is connected to the ammonia water station 5.

[0023] In this invention, the feeding pipeline 21, the dilute ammonia water pipeline 22, the low-pressure feed pipeline 31, and the low-pressure venting pipeline 32 are all equipped with at least one manual valve 6.

[0024] The present invention also provides an ammoniation method for urea production using the ammonia stripping process employing the above-mentioned low-pressure system, comprising the following steps: (1) A medium-pressure inert gas scrubbing tower is used to prepare dilute ammonia water, and the concentration of dilute ammonia water is controlled at 25-35%; (2) The dilute ammonia water in the medium-pressure inert gas scrubbing tower is discharged from the bottom of the tower and sent to the low-pressure system in sequence through the feed pipeline and the dilute ammonia water pipeline using the ammonia water pump; (3) In the low-pressure system, dilute ammonia water is introduced from the dilute ammonia water pipeline and merged with the low-pressure washing water in the low-pressure feed pipeline. It is then introduced into the low-pressure ammonium carbonate liquid storage tank for cooling treatment.

[0025] Using the feed pipeline from the ammonia pump outlet to the medium-pressure absorption tower, a dilute ammonia water pipeline is configured at the drain outlet behind the liquid level regulating valve and in front of the manual valve of the medium-pressure inert gas scrubbing tower. The dilute ammonia water pipeline is connected to the front end of the low-pressure scrubbing water regulating valve of the low-pressure ammonium bicarbonate liquid storage tank. The dilute ammonia water configured through the medium-pressure inert gas scrubbing tower can be pumped to the low-pressure system and pre-cooled by the condenser configured in the low-pressure ammonium bicarbonate liquid storage tank before entering the low-pressure ammonium bicarbonate liquid storage tank for storage.

[0026] In this invention, a low-pressure venting pressure regulating valve is used to regulate the pressure of the low-pressure system, and the low-pressure system is regulated and controlled by the low-pressure venting pressure regulating valve.

[0027] Example 1 In this embodiment, the low-pressure system of the ammonia stripping urea production process includes a low-pressure ammonium bicarbonate liquid storage tank 3. The feed end of the low-pressure ammonium bicarbonate liquid storage tank 3 is connected to a medium-pressure inert gas scrubbing tower 1. Specifically, an ammonia water pump 2 is connected to the bottom of the medium-pressure inert gas scrubbing tower 1. A feeding pipeline 21 and a dilute ammonia water pipeline 22 are connected sequentially between the ammonia water pump 2 and the low-pressure ammonium bicarbonate liquid storage tank 3. The feed end of the feeding pipeline 21 is connected to the ammonia water pump 2, and the discharge end of the feeding pipeline 21 is connected to a medium-pressure absorption tower 4. One end of the dilute ammonia water pipeline 22 is connected to the middle section of the feeding pipeline 21, and the other end of the dilute ammonia water pipeline 22 is connected to the low-pressure ammonium bicarbonate liquid storage tank 3.

[0028] The low-pressure ammonium bicarbonate solution storage tank 3 is equipped with a low-pressure feed pipeline 31. One end of the dilute ammonia water pipeline 22, near the low-pressure ammonium bicarbonate solution storage tank 3, is connected to the middle section of the low-pressure feed pipeline 31. The low-pressure feed pipeline 31 is equipped with a low-pressure washing water regulating valve 311, located on the side away from the connection point between the dilute ammonia water pipeline 22 and the low-pressure feed pipeline 31. A low-pressure vent pipeline 32 is also installed at the top of the low-pressure ammonium bicarbonate solution storage tank 3, and this vent pipeline 32 is equipped with a low-pressure vent pressure regulating valve 321.

[0029] The feed pipeline 21 is equipped with an inert gas scrubbing tower level regulating valve 211. The inert gas scrubbing tower level regulating valve 211 is located on the side near the ammonia pump 2 at the connection between the feed pipeline 21 and the dilute ammonia water pipeline 22. The end of the feed pipeline 21 near the ammonia pump 2 is also connected to the return pipeline 23 and the ammonia delivery pipeline 24. The end of the return pipeline 23 away from the feed pipeline 21 is connected to the medium-pressure inert gas scrubbing tower 1, and the end of the ammonia delivery pipeline 24 away from the feed pipeline 21 is connected to the ammonia station 5.

[0030] In addition, the feeding pipeline 21, the dilute ammonia water pipeline 22, the low-pressure feed pipeline 31, and the low-pressure venting pipeline 32 are all equipped with manual valves 6.

[0031] Dilute ammonia water is prepared in the medium-pressure inert gas scrubbing tower 1 and sent out by the ammonia water pump 2. It is then sent to the low-pressure ammonium carbonate liquid storage tank 3 through the feeding pipeline 21 and the dilute ammonia water pipeline 22. After that, it is cooled and treated by the condenser configured in the low-pressure ammonium carbonate liquid storage tank 3.

[0032] Using the above method for ammoniation treatment, the amount of dilute ammonia water required for each urea plant start-up phase is about 80 tons (based on 30wt% dilute ammonia water), which can reduce the actual concentration to 22.5wt%, corresponding to a reduction of about 4-5 tons of ammonia loss due to venting, and a reduction of production costs of tens of thousands of yuan.

[0033] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A low-pressure system for ammonia stripping urea production process, characterized in that, It includes a medium-pressure inert gas scrubbing tower (1), the bottom of which is connected to an ammonia water pump (2), and the outlet end of the ammonia water pump (2) is connected to a low-pressure ammonium bicarbonate liquid storage tank (3). The ammonia pump (2) and the low-pressure ammonium carbonate liquid storage tank (3) are connected in sequence by a feeding pipeline (21) and a dilute ammonia pipeline (22). The discharge end of the feeding pipeline (21) is connected to the medium-pressure absorption tower (4). The end of the dilute ammonia pipeline (22) away from the low-pressure ammonium carbonate liquid storage tank (3) is connected to the middle section of the feeding pipeline (21).

2. The low-pressure system for the ammonia stripping urea production process according to claim 1, characterized in that, The low-pressure ammonium bicarbonate liquid storage tank (3) is equipped with a low-pressure feed pipeline (31), and the end of the dilute ammonia water pipeline (22) near the low-pressure ammonium bicarbonate liquid storage tank (3) is connected to the middle section of the low-pressure feed pipeline (31).

3. The low-pressure system for the ammonia stripping urea production process according to claim 2, characterized in that, The low-pressure feed line (31) is equipped with a low-pressure washing water regulating valve (311), which is located on the side away from the low-pressure ammonium carbonate liquid storage tank (3) at the connection between the dilute ammonia water line (22) and the low-pressure feed line (31).

4. The low-pressure system for the ammonia stripping urea production process according to claim 3, characterized in that, The top of the low-pressure ammonium bicarbonate liquid storage tank (3) is also equipped with a low-pressure venting pipeline (32), and the low-pressure venting pipeline (32) is equipped with a low-pressure venting pressure regulating valve (321).

5. The low-pressure system for the ammonia stripping urea production process according to claim 4, characterized in that, The feeding pipeline (21) is equipped with an inert gas scrubbing tower level regulating valve (211), which is located near the ammonia pump (2) at the connection between the feeding pipeline (21) and the dilute ammonia water pipeline (22).

6. The low-pressure system for the ammonia stripping urea production process according to claim 5, characterized in that, The end of the feed pipeline (21) near the ammonia pump (2) is also connected to the return pipeline (23) and the ammonia delivery pipeline (24). The end of the return pipeline (23) away from the feed pipeline (21) is connected to the medium-pressure inert gas scrubbing tower (1). The end of the ammonia delivery pipeline (24) away from the feed pipeline (21) is connected to the ammonia station (5).

7. The low-pressure system for the ammonia stripping urea production process according to claim 5, characterized in that, The feeding pipeline (21), the dilute ammonia water pipeline (22), the low-pressure feed pipeline (31) and the low-pressure venting pipeline (32) are each equipped with at least one manual valve (6).

8. The ammoniation method for ammonia stripping urea production using the low-pressure system of the ammonia stripping urea production process according to claim 4, characterized in that, Includes the following steps: S1 uses a medium-pressure inert gas scrubbing tower to prepare dilute ammonia water; S2 discharges the dilute ammonia water from the bottom of the medium-pressure inert gas scrubbing tower and sends it to the low-pressure system via the ammonia water pump, through the feed pipeline and the dilute ammonia water pipeline. In the low-pressure system, dilute ammonia water is introduced from the dilute ammonia water pipeline and merged with the low-pressure washing water in the low-pressure feed pipeline. The mixture is then introduced into the low-pressure ammonium bicarbonate liquid storage tank for cooling.

9. The ammoniation method for urea production via ammonia stripping according to claim 8, characterized in that, The concentration of dilute ammonia solution should be controlled at 25-35%.

10. The ammoniation method for urea production via ammonia stripping according to claim 8, characterized in that, The pressure of the low-pressure system is regulated by a low-pressure venting pressure regulating valve.

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